diff --git a/news/7cecf5ba-92a1-49a9-85f0-07a4dd8aca46.trivial.rst b/news/7cecf5ba-92a1-49a9-85f0-07a4dd8aca46.trivial.rst
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/setup.cfg b/setup.cfg
index 2a1c574c8c5..ae6aa38d8b2 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -51,10 +51,6 @@ follow_imports = skip
 [mypy-pip._vendor.requests.*]
 follow_imports = skip
 
-# TODO: The following option should be removed at some point in the future.
-[mypy-tests.functional.*]
-allow_untyped_defs = True
-
 [tool:pytest]
 addopts = --ignore src/pip/_vendor --ignore tests/tests_cache -r aR --color=yes
 xfail_strict = True
diff --git a/tests/conftest.py b/tests/conftest.py
index 076aeaf1983..f663b96ea46 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -36,7 +36,13 @@
 from .lib.compat import nullcontext
 
 if TYPE_CHECKING:
+    from typing import Protocol
+
     from wsgi import WSGIApplication
+else:
+    # TODO: Protocol was introduced in Python 3.8. Remove this branch when
+    # dropping support for Python 3.7.
+    Protocol = object
 
 
 def pytest_addoption(parser: Parser) -> None:
@@ -442,10 +448,17 @@ def with_wheel(virtualenv: VirtualEnvironment, wheel_install: Path) -> None:
     install_egg_link(virtualenv, "wheel", wheel_install)
 
 
+class ScriptFactory(Protocol):
+    def __call__(
+        self, tmpdir: Path, virtualenv: Optional[VirtualEnvironment] = None
+    ) -> PipTestEnvironment:
+        ...
+
+
 @pytest.fixture(scope="session")
 def script_factory(
     virtualenv_factory: Callable[[Path], VirtualEnvironment], deprecated_python: bool
-) -> Callable[[Path, Optional[VirtualEnvironment]], PipTestEnvironment]:
+) -> ScriptFactory:
     def factory(
         tmpdir: Path, virtualenv: Optional[VirtualEnvironment] = None
     ) -> PipTestEnvironment:
@@ -533,8 +546,11 @@ def deprecated_python() -> bool:
     return sys.version_info[:2] in []
 
 
+CertFactory = Callable[[], str]
+
+
 @pytest.fixture(scope="session")
-def cert_factory(tmpdir_factory: pytest.TempdirFactory) -> Callable[[], str]:
+def cert_factory(tmpdir_factory: pytest.TempdirFactory) -> CertFactory:
     def factory() -> str:
         """Returns path to cert/key file."""
         output_path = Path(str(tmpdir_factory.mktemp("certs"))) / "cert.pem"
diff --git a/tests/functional/test_broken_stdout.py b/tests/functional/test_broken_stdout.py
index 0d261283813..e7313244379 100644
--- a/tests/functional/test_broken_stdout.py
+++ b/tests/functional/test_broken_stdout.py
@@ -1,18 +1,25 @@
 import os
 import subprocess
+from typing import List, Tuple
+
+from tests.lib.path import Path
 
 _BROKEN_STDOUT_RETURN_CODE = 120
 
 
-def setup_broken_stdout_test(args, deprecated_python):
+def setup_broken_stdout_test(
+    args: List[str], deprecated_python: bool
+) -> Tuple[str, int]:
     proc = subprocess.Popen(
         args,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
     )
     # Call close() on stdout to cause a broken pipe.
+    assert proc.stdout is not None
     proc.stdout.close()
     returncode = proc.wait()
+    assert proc.stderr is not None
     stderr = proc.stderr.read().decode("utf-8")
 
     expected_msg = "ERROR: Pipe to stdout was broken"
@@ -24,7 +31,7 @@ def setup_broken_stdout_test(args, deprecated_python):
     return stderr, returncode
 
 
-def test_broken_stdout_pipe(deprecated_python):
+def test_broken_stdout_pipe(deprecated_python: bool) -> None:
     """
     Test a broken pipe to stdout.
     """
@@ -40,7 +47,7 @@ def test_broken_stdout_pipe(deprecated_python):
     assert returncode == _BROKEN_STDOUT_RETURN_CODE
 
 
-def test_broken_stdout_pipe__log_option(deprecated_python, tmpdir):
+def test_broken_stdout_pipe__log_option(deprecated_python: bool, tmpdir: Path) -> None:
     """
     Test a broken pipe to stdout when --log is passed.
     """
@@ -57,7 +64,7 @@ def test_broken_stdout_pipe__log_option(deprecated_python, tmpdir):
     assert returncode == _BROKEN_STDOUT_RETURN_CODE
 
 
-def test_broken_stdout_pipe__verbose(deprecated_python):
+def test_broken_stdout_pipe__verbose(deprecated_python: bool) -> None:
     """
     Test a broken pipe to stdout with verbose logging enabled.
     """
diff --git a/tests/functional/test_build_env.py b/tests/functional/test_build_env.py
index 1b97143a086..f846b305435 100644
--- a/tests/functional/test_build_env.py
+++ b/tests/functional/test_build_env.py
@@ -1,16 +1,26 @@
 from textwrap import dedent
+from typing import Optional
 
 import pytest
 
 from pip._internal.build_env import BuildEnvironment
-from tests.lib import create_basic_wheel_for_package, make_test_finder
+from tests.lib import (
+    PipTestEnvironment,
+    TestPipResult,
+    create_basic_wheel_for_package,
+    make_test_finder,
+)
 
 
-def indent(text, prefix):
+def indent(text: str, prefix: str) -> str:
     return "\n".join((prefix if line else "") + line for line in text.split("\n"))
 
 
-def run_with_build_env(script, setup_script_contents, test_script_contents=None):
+def run_with_build_env(
+    script: PipTestEnvironment,
+    setup_script_contents: str,
+    test_script_contents: Optional[str] = None,
+) -> TestPipResult:
     build_env_script = script.scratch_path / "build_env.py"
     build_env_script.write_text(
         dedent(
@@ -66,13 +76,16 @@ def run_with_build_env(script, setup_script_contents, test_script_contents=None)
     return script.run(*args)
 
 
-def test_build_env_allow_empty_requirements_install():
+def test_build_env_allow_empty_requirements_install() -> None:
+    finder = make_test_finder()
     build_env = BuildEnvironment()
     for prefix in ("normal", "overlay"):
-        build_env.install_requirements(None, [], prefix, None)
+        build_env.install_requirements(
+            finder, [], prefix, "Installing build dependencies"
+        )
 
 
-def test_build_env_allow_only_one_install(script):
+def test_build_env_allow_only_one_install(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "foo", "1.0")
     create_basic_wheel_for_package(script, "bar", "1.0")
     finder = make_test_finder(find_links=[script.scratch_path])
@@ -91,7 +104,7 @@ def test_build_env_allow_only_one_install(script):
             )
 
 
-def test_build_env_requirements_check(script):
+def test_build_env_requirements_check(script: PipTestEnvironment) -> None:
 
     create_basic_wheel_for_package(script, "foo", "2.0")
     create_basic_wheel_for_package(script, "bar", "1.0")
@@ -152,7 +165,7 @@ def test_build_env_requirements_check(script):
     )
 
 
-def test_build_env_overlay_prefix_has_priority(script):
+def test_build_env_overlay_prefix_has_priority(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "pkg", "2.0")
     create_basic_wheel_for_package(script, "pkg", "4.3")
     result = run_with_build_env(
@@ -171,7 +184,7 @@ def test_build_env_overlay_prefix_has_priority(script):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_build_env_isolation(script):
+def test_build_env_isolation(script: PipTestEnvironment) -> None:
 
     # Create dummy `pkg` wheel.
     pkg_whl = create_basic_wheel_for_package(script, "pkg", "1.0")
diff --git a/tests/functional/test_cache.py b/tests/functional/test_cache.py
index ef3f2e4c849..712e08a85cc 100644
--- a/tests/functional/test_cache.py
+++ b/tests/functional/test_cache.py
@@ -1,12 +1,15 @@
 import os
 import shutil
 from glob import glob
+from typing import Callable, List, Tuple
 
 import pytest
 
+from tests.lib import PipTestEnvironment, TestPipResult
+
 
 @pytest.fixture
-def cache_dir(script):
+def cache_dir(script: PipTestEnvironment) -> str:
     result = script.run(
         "python",
         "-c",
@@ -16,17 +19,17 @@ def cache_dir(script):
 
 
 @pytest.fixture
-def http_cache_dir(cache_dir):
+def http_cache_dir(cache_dir: str) -> str:
     return os.path.normcase(os.path.join(cache_dir, "http"))
 
 
 @pytest.fixture
-def wheel_cache_dir(cache_dir):
+def wheel_cache_dir(cache_dir: str) -> str:
     return os.path.normcase(os.path.join(cache_dir, "wheels"))
 
 
 @pytest.fixture
-def http_cache_files(http_cache_dir):
+def http_cache_files(http_cache_dir: str) -> List[str]:
     destination = os.path.join(http_cache_dir, "arbitrary", "pathname")
 
     if not os.path.exists(destination):
@@ -40,7 +43,7 @@ def http_cache_files(http_cache_dir):
 
 
 @pytest.fixture
-def wheel_cache_files(wheel_cache_dir):
+def wheel_cache_files(wheel_cache_dir: str) -> List[str]:
     destination = os.path.join(wheel_cache_dir, "arbitrary", "pathname")
 
     if not os.path.exists(destination):
@@ -54,7 +57,7 @@ def wheel_cache_files(wheel_cache_dir):
 
 
 @pytest.fixture
-def populate_http_cache(http_cache_dir):
+def populate_http_cache(http_cache_dir: str) -> List[Tuple[str, str]]:
     destination = os.path.join(http_cache_dir, "arbitrary", "pathname")
     os.makedirs(destination)
 
@@ -72,7 +75,7 @@ def populate_http_cache(http_cache_dir):
 
 
 @pytest.fixture
-def populate_wheel_cache(wheel_cache_dir):
+def populate_wheel_cache(wheel_cache_dir: str) -> List[Tuple[str, str]]:
     destination = os.path.join(wheel_cache_dir, "arbitrary", "pathname")
     os.makedirs(destination)
 
@@ -91,12 +94,12 @@ def populate_wheel_cache(wheel_cache_dir):
 
 
 @pytest.fixture
-def empty_wheel_cache(wheel_cache_dir):
+def empty_wheel_cache(wheel_cache_dir: str) -> None:
     if os.path.exists(wheel_cache_dir):
         shutil.rmtree(wheel_cache_dir)
 
 
-def list_matches_wheel(wheel_name, result):
+def list_matches_wheel(wheel_name: str, result: TestPipResult) -> bool:
     """Returns True if any line in `result`, which should be the output of
     a `pip cache list` call, matches `wheel_name`.
 
@@ -107,7 +110,7 @@ def list_matches_wheel(wheel_name, result):
     return any(map(lambda l: l.startswith(expected), lines))
 
 
-def list_matches_wheel_abspath(wheel_name, result):
+def list_matches_wheel_abspath(wheel_name: str, result: TestPipResult) -> bool:
     """Returns True if any line in `result`, which should be the output of
     a `pip cache list --format=abspath` call, is a valid path and belongs to
     `wheel_name`.
@@ -124,8 +127,11 @@ def list_matches_wheel_abspath(wheel_name, result):
     )
 
 
+RemoveMatches = Callable[[str, TestPipResult], bool]
+
+
 @pytest.fixture
-def remove_matches_http(http_cache_dir):
+def remove_matches_http(http_cache_dir: str) -> RemoveMatches:
     """Returns True if any line in `result`, which should be the output of
     a `pip cache purge` call, matches `http_filename`.
 
@@ -133,7 +139,7 @@ def remove_matches_http(http_cache_dir):
     `Removed <http files cache dir>/arbitrary/pathname/aaaaaaaaa`.
     """
 
-    def _remove_matches_http(http_filename, result):
+    def _remove_matches_http(http_filename: str, result: TestPipResult) -> bool:
         lines = result.stdout.splitlines()
 
         # The "/arbitrary/pathname/" bit is an implementation detail of how
@@ -151,7 +157,7 @@ def _remove_matches_http(http_filename, result):
 
 
 @pytest.fixture
-def remove_matches_wheel(wheel_cache_dir):
+def remove_matches_wheel(wheel_cache_dir: str) -> RemoveMatches:
     """Returns True if any line in `result`, which should be the output of
     a `pip cache remove`/`pip cache purge` call, matches `wheel_name`.
 
@@ -159,7 +165,7 @@ def remove_matches_wheel(wheel_cache_dir):
     `Removed <wheel cache dir>/arbitrary/pathname/foo-1.2.3-py3-none-any.whl`.
     """
 
-    def _remove_matches_wheel(wheel_name, result):
+    def _remove_matches_wheel(wheel_name: str, result: TestPipResult) -> bool:
         lines = result.stdout.splitlines()
 
         wheel_filename = f"{wheel_name}-py3-none-any.whl"
@@ -178,13 +184,13 @@ def _remove_matches_wheel(wheel_name, result):
     return _remove_matches_wheel
 
 
-def test_cache_dir(script, cache_dir):
+def test_cache_dir(script: PipTestEnvironment, cache_dir: str) -> None:
     result = script.pip("cache", "dir")
 
     assert os.path.normcase(cache_dir) == result.stdout.strip()
 
 
-def test_cache_dir_too_many_args(script, cache_dir):
+def test_cache_dir_too_many_args(script: PipTestEnvironment, cache_dir: str) -> None:
     result = script.pip("cache", "dir", "aaa", expect_error=True)
 
     assert result.stdout == ""
@@ -195,7 +201,12 @@ def test_cache_dir_too_many_args(script, cache_dir):
 
 
 @pytest.mark.usefixtures("populate_http_cache", "populate_wheel_cache")
-def test_cache_info(script, http_cache_dir, wheel_cache_dir, wheel_cache_files):
+def test_cache_info(
+    script: PipTestEnvironment,
+    http_cache_dir: str,
+    wheel_cache_dir: str,
+    wheel_cache_files: List[str],
+) -> None:
     result = script.pip("cache", "info")
 
     assert f"Package index page cache location: {http_cache_dir}" in result.stdout
@@ -205,7 +216,7 @@ def test_cache_info(script, http_cache_dir, wheel_cache_dir, wheel_cache_files):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_list(script):
+def test_cache_list(script: PipTestEnvironment) -> None:
     """Running `pip cache list` should return exactly what the
     populate_wheel_cache fixture adds."""
     result = script.pip("cache", "list")
@@ -217,7 +228,7 @@ def test_cache_list(script):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_list_abspath(script):
+def test_cache_list_abspath(script: PipTestEnvironment) -> None:
     """Running `pip cache list --format=abspath` should return full
     paths of exactly what the populate_wheel_cache fixture adds."""
     result = script.pip("cache", "list", "--format=abspath")
@@ -229,7 +240,7 @@ def test_cache_list_abspath(script):
 
 
 @pytest.mark.usefixtures("empty_wheel_cache")
-def test_cache_list_with_empty_cache(script):
+def test_cache_list_with_empty_cache(script: PipTestEnvironment) -> None:
     """Running `pip cache list` with an empty cache should print
     "Nothing cached." and exit."""
     result = script.pip("cache", "list")
@@ -237,7 +248,7 @@ def test_cache_list_with_empty_cache(script):
 
 
 @pytest.mark.usefixtures("empty_wheel_cache")
-def test_cache_list_with_empty_cache_abspath(script):
+def test_cache_list_with_empty_cache_abspath(script: PipTestEnvironment) -> None:
     """Running `pip cache list --format=abspath` with an empty cache should not
     print anything and exit."""
     result = script.pip("cache", "list", "--format=abspath")
@@ -245,7 +256,7 @@ def test_cache_list_with_empty_cache_abspath(script):
 
 
 @pytest.mark.usefixtures("empty_wheel_cache")
-def test_cache_purge_with_empty_cache(script):
+def test_cache_purge_with_empty_cache(script: PipTestEnvironment) -> None:
     """Running `pip cache purge` with an empty cache should print a warning
     and exit without an error code."""
     result = script.pip("cache", "purge", allow_stderr_warning=True)
@@ -254,7 +265,7 @@ def test_cache_purge_with_empty_cache(script):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_remove_with_bad_pattern(script):
+def test_cache_remove_with_bad_pattern(script: PipTestEnvironment) -> None:
     """Running `pip cache remove` with a bad pattern should print a warning
     and exit without an error code."""
     result = script.pip("cache", "remove", "aaa", allow_stderr_warning=True)
@@ -262,13 +273,13 @@ def test_cache_remove_with_bad_pattern(script):
     assert result.stdout == "Files removed: 0\n"
 
 
-def test_cache_list_too_many_args(script):
+def test_cache_list_too_many_args(script: PipTestEnvironment) -> None:
     """Passing `pip cache list` too many arguments should cause an error."""
     script.pip("cache", "list", "aaa", "bbb", expect_error=True)
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_list_name_match(script):
+def test_cache_list_name_match(script: PipTestEnvironment) -> None:
     """Running `pip cache list zzz` should list zzz-4.5.6, zzz-4.5.7,
     zzz-7.8.9, but nothing else."""
     result = script.pip("cache", "list", "zzz", "--verbose")
@@ -280,7 +291,7 @@ def test_cache_list_name_match(script):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_list_name_match_abspath(script):
+def test_cache_list_name_match_abspath(script: PipTestEnvironment) -> None:
     """Running `pip cache list zzz --format=abspath` should list paths of
     zzz-4.5.6, zzz-4.5.7, zzz-7.8.9, but nothing else."""
     result = script.pip("cache", "list", "zzz", "--format=abspath", "--verbose")
@@ -292,7 +303,7 @@ def test_cache_list_name_match_abspath(script):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_list_name_and_version_match(script):
+def test_cache_list_name_and_version_match(script: PipTestEnvironment) -> None:
     """Running `pip cache list zzz-4.5.6` should list zzz-4.5.6, but
     nothing else."""
     result = script.pip("cache", "list", "zzz-4.5.6", "--verbose")
@@ -304,7 +315,7 @@ def test_cache_list_name_and_version_match(script):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_list_name_and_version_match_abspath(script):
+def test_cache_list_name_and_version_match_abspath(script: PipTestEnvironment) -> None:
     """Running `pip cache list zzz-4.5.6 --format=abspath` should list path of
     zzz-4.5.6, but nothing else."""
     result = script.pip("cache", "list", "zzz-4.5.6", "--format=abspath", "--verbose")
@@ -316,18 +327,20 @@ def test_cache_list_name_and_version_match_abspath(script):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_remove_no_arguments(script):
+def test_cache_remove_no_arguments(script: PipTestEnvironment) -> None:
     """Running `pip cache remove` with no arguments should cause an error."""
     script.pip("cache", "remove", expect_error=True)
 
 
-def test_cache_remove_too_many_args(script):
+def test_cache_remove_too_many_args(script: PipTestEnvironment) -> None:
     """Passing `pip cache remove` too many arguments should cause an error."""
     script.pip("cache", "remove", "aaa", "bbb", expect_error=True)
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_remove_name_match(script, remove_matches_wheel):
+def test_cache_remove_name_match(
+    script: PipTestEnvironment, remove_matches_wheel: RemoveMatches
+) -> None:
     """Running `pip cache remove zzz` should remove zzz-4.5.6 and zzz-7.8.9,
     but nothing else."""
     result = script.pip("cache", "remove", "zzz", "--verbose")
@@ -339,7 +352,9 @@ def test_cache_remove_name_match(script, remove_matches_wheel):
 
 
 @pytest.mark.usefixtures("populate_wheel_cache")
-def test_cache_remove_name_and_version_match(script, remove_matches_wheel):
+def test_cache_remove_name_and_version_match(
+    script: PipTestEnvironment, remove_matches_wheel: RemoveMatches
+) -> None:
     """Running `pip cache remove zzz-4.5.6` should remove zzz-4.5.6, but
     nothing else."""
     result = script.pip("cache", "remove", "zzz-4.5.6", "--verbose")
@@ -351,7 +366,11 @@ def test_cache_remove_name_and_version_match(script, remove_matches_wheel):
 
 
 @pytest.mark.usefixtures("populate_http_cache", "populate_wheel_cache")
-def test_cache_purge(script, remove_matches_http, remove_matches_wheel):
+def test_cache_purge(
+    script: PipTestEnvironment,
+    remove_matches_http: RemoveMatches,
+    remove_matches_wheel: RemoveMatches,
+) -> None:
     """Running `pip cache purge` should remove all cached http files and
     wheels."""
     result = script.pip("cache", "purge", "--verbose")
@@ -367,7 +386,11 @@ def test_cache_purge(script, remove_matches_http, remove_matches_wheel):
 
 
 @pytest.mark.usefixtures("populate_http_cache", "populate_wheel_cache")
-def test_cache_purge_too_many_args(script, http_cache_files, wheel_cache_files):
+def test_cache_purge_too_many_args(
+    script: PipTestEnvironment,
+    http_cache_files: List[str],
+    wheel_cache_files: List[str],
+) -> None:
     """Running `pip cache purge aaa` should raise an error and remove no
     cached http files or wheels."""
     result = script.pip("cache", "purge", "aaa", "--verbose", expect_error=True)
@@ -383,7 +406,9 @@ def test_cache_purge_too_many_args(script, http_cache_files, wheel_cache_files):
 
 
 @pytest.mark.parametrize("command", ["info", "list", "remove", "purge"])
-def test_cache_abort_when_no_cache_dir(script, command):
+def test_cache_abort_when_no_cache_dir(
+    script: PipTestEnvironment, command: str
+) -> None:
     """Running any pip cache command when cache is disabled should
     abort and log an informative error"""
     result = script.pip("cache", command, "--no-cache-dir", expect_error=True)
diff --git a/tests/functional/test_check.py b/tests/functional/test_check.py
index d039e52676a..e2b1c60ef3a 100644
--- a/tests/functional/test_check.py
+++ b/tests/functional/test_check.py
@@ -1,7 +1,9 @@
-from tests.lib import create_test_package_with_setup
+from typing import Collection
 
+from tests.lib import PipTestEnvironment, create_test_package_with_setup
 
-def matches_expected_lines(string, expected_lines):
+
+def matches_expected_lines(string: str, expected_lines: Collection[str]) -> bool:
     # Ignore empty lines
     output_lines = list(filter(None, string.splitlines()))
     # We'll match the last n lines, given n lines to match.
@@ -10,7 +12,7 @@ def matches_expected_lines(string, expected_lines):
     return set(last_few_output_lines) == set(expected_lines)
 
 
-def test_basic_check_clean(script):
+def test_basic_check_clean(script: PipTestEnvironment) -> None:
     """On a clean environment, check should print a helpful message."""
     result = script.pip("check")
 
@@ -19,7 +21,7 @@ def test_basic_check_clean(script):
     assert result.returncode == 0
 
 
-def test_basic_check_missing_dependency(script):
+def test_basic_check_missing_dependency(script: PipTestEnvironment) -> None:
     # Setup a small project
     pkga_path = create_test_package_with_setup(
         script,
@@ -38,7 +40,7 @@ def test_basic_check_missing_dependency(script):
     assert result.returncode == 1
 
 
-def test_basic_check_broken_dependency(script):
+def test_basic_check_broken_dependency(script: PipTestEnvironment) -> None:
     # Setup pkga depending on pkgb>=1.0
     pkga_path = create_test_package_with_setup(
         script,
@@ -72,7 +74,9 @@ def test_basic_check_broken_dependency(script):
     assert result.returncode == 1
 
 
-def test_basic_check_broken_dependency_and_missing_dependency(script):
+def test_basic_check_broken_dependency_and_missing_dependency(
+    script: PipTestEnvironment,
+) -> None:
     pkga_path = create_test_package_with_setup(
         script,
         name="pkga",
@@ -105,7 +109,7 @@ def test_basic_check_broken_dependency_and_missing_dependency(script):
     assert result.returncode == 1
 
 
-def test_check_complicated_name_missing(script):
+def test_check_complicated_name_missing(script: PipTestEnvironment) -> None:
     package_a_path = create_test_package_with_setup(
         script,
         name="package_A",
@@ -123,7 +127,7 @@ def test_check_complicated_name_missing(script):
     assert result.returncode == 1
 
 
-def test_check_complicated_name_broken(script):
+def test_check_complicated_name_broken(script: PipTestEnvironment) -> None:
     package_a_path = create_test_package_with_setup(
         script,
         name="package_A",
@@ -157,7 +161,7 @@ def test_check_complicated_name_broken(script):
     assert result.returncode == 1
 
 
-def test_check_complicated_name_clean(script):
+def test_check_complicated_name_clean(script: PipTestEnvironment) -> None:
     package_a_path = create_test_package_with_setup(
         script,
         name="package_A",
@@ -187,7 +191,7 @@ def test_check_complicated_name_clean(script):
     assert result.returncode == 0
 
 
-def test_check_considers_conditional_reqs(script):
+def test_check_considers_conditional_reqs(script: PipTestEnvironment) -> None:
     package_a_path = create_test_package_with_setup(
         script,
         name="package_A",
@@ -207,7 +211,9 @@ def test_check_considers_conditional_reqs(script):
     assert result.returncode == 1
 
 
-def test_check_development_versions_are_also_considered(script):
+def test_check_development_versions_are_also_considered(
+    script: PipTestEnvironment,
+) -> None:
     # Setup pkga depending on pkgb>=1.0
     pkga_path = create_test_package_with_setup(
         script,
@@ -240,7 +246,7 @@ def test_check_development_versions_are_also_considered(script):
     assert result.returncode == 0
 
 
-def test_basic_check_broken_metadata(script):
+def test_basic_check_broken_metadata(script: PipTestEnvironment) -> None:
     # Create some corrupt metadata
     dist_info_dir = script.site_packages_path / "pkga-1.0.dist-info"
     dist_info_dir.mkdir()
@@ -258,7 +264,7 @@ def test_basic_check_broken_metadata(script):
     assert result.returncode == 1
 
 
-def test_check_skip_work_dir_pkg(script):
+def test_check_skip_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that check should not include package
     present in working directory
@@ -280,7 +286,7 @@ def test_check_skip_work_dir_pkg(script):
     assert result.returncode == 0
 
 
-def test_check_include_work_dir_pkg(script):
+def test_check_include_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that check should include package in working directory
     if working directory is added in PYTHONPATH
diff --git a/tests/functional/test_cli.py b/tests/functional/test_cli.py
index e9d4157b9ba..3e8570359bb 100644
--- a/tests/functional/test_cli.py
+++ b/tests/functional/test_cli.py
@@ -4,6 +4,8 @@
 
 import pytest
 
+from tests.lib import PipTestEnvironment
+
 
 @pytest.mark.parametrize(
     "entrypoint",
@@ -13,7 +15,7 @@
         ("fake_pip = pip:main",),
     ],
 )
-def test_entrypoints_work(entrypoint, script):
+def test_entrypoints_work(entrypoint: str, script: PipTestEnvironment) -> None:
     fake_pkg = script.temp_path / "fake_pkg"
     fake_pkg.mkdir()
     fake_pkg.joinpath("setup.py").write_text(
diff --git a/tests/functional/test_completion.py b/tests/functional/test_completion.py
index 7183cb1269c..927ec7ba631 100644
--- a/tests/functional/test_completion.py
+++ b/tests/functional/test_completion.py
@@ -1,10 +1,21 @@
 import os
 import sys
+from typing import TYPE_CHECKING, Optional, Tuple
 
 import pytest
 
+from tests.conftest import ScriptFactory
+from tests.lib import PipTestEnvironment, TestData, TestPipResult
 from tests.lib.path import Path
 
+if TYPE_CHECKING:
+    from typing import Protocol
+else:
+    # TODO: Protocol was introduced in Python 3.8. Remove this branch when
+    # dropping support for Python 3.7.
+    Protocol = object
+
+
 COMPLETION_FOR_SUPPORTED_SHELLS_TESTS = (
     (
         "bash",
@@ -47,7 +58,12 @@
 
 
 @pytest.fixture(scope="session")
-def script_with_launchers(tmpdir_factory, script_factory, common_wheels, pip_src):
+def script_with_launchers(
+    tmpdir_factory: pytest.TempdirFactory,
+    script_factory: ScriptFactory,
+    common_wheels: Path,
+    pip_src: Path,
+) -> PipTestEnvironment:
     tmpdir = Path(str(tmpdir_factory.mktemp("script_with_launchers")))
     script = script_factory(tmpdir.joinpath("workspace"))
     # Re-install pip so we get the launchers.
@@ -60,7 +76,9 @@ def script_with_launchers(tmpdir_factory, script_factory, common_wheels, pip_src
     COMPLETION_FOR_SUPPORTED_SHELLS_TESTS,
     ids=[t[0] for t in COMPLETION_FOR_SUPPORTED_SHELLS_TESTS],
 )
-def test_completion_for_supported_shells(script_with_launchers, shell, completion):
+def test_completion_for_supported_shells(
+    script_with_launchers: PipTestEnvironment, shell: str, completion: str
+) -> None:
     """
     Test getting completion for bash shell
     """
@@ -69,17 +87,30 @@ def test_completion_for_supported_shells(script_with_launchers, shell, completio
 
 
 @pytest.fixture(scope="session")
-def autocomplete_script(tmpdir_factory, script_factory):
+def autocomplete_script(
+    tmpdir_factory: pytest.TempdirFactory, script_factory: ScriptFactory
+) -> PipTestEnvironment:
     tmpdir = Path(str(tmpdir_factory.mktemp("autocomplete_script")))
     return script_factory(tmpdir.joinpath("workspace"))
 
 
+class DoAutocomplete(Protocol):
+    def __call__(
+        self, words: str, cword: str, cwd: Optional[str] = None
+    ) -> Tuple[TestPipResult, PipTestEnvironment]:
+        ...
+
+
 @pytest.fixture
-def autocomplete(autocomplete_script, monkeypatch):
+def autocomplete(
+    autocomplete_script: PipTestEnvironment, monkeypatch: pytest.MonkeyPatch
+) -> DoAutocomplete:
     monkeypatch.setattr(autocomplete_script, "environ", os.environ.copy())
     autocomplete_script.environ["PIP_AUTO_COMPLETE"] = "1"
 
-    def do_autocomplete(words, cword, cwd=None):
+    def do_autocomplete(
+        words: str, cword: str, cwd: Optional[str] = None
+    ) -> Tuple[TestPipResult, PipTestEnvironment]:
         autocomplete_script.environ["COMP_WORDS"] = words
         autocomplete_script.environ["COMP_CWORD"] = cword
         result = autocomplete_script.run(
@@ -96,7 +127,7 @@ def do_autocomplete(words, cword, cwd=None):
     return do_autocomplete
 
 
-def test_completion_for_unknown_shell(autocomplete_script):
+def test_completion_for_unknown_shell(autocomplete_script: PipTestEnvironment) -> None:
     """
     Test getting completion for an unknown shell
     """
@@ -105,7 +136,7 @@ def test_completion_for_unknown_shell(autocomplete_script):
     assert error_msg in result.stderr, "tests for an unknown shell failed"
 
 
-def test_completion_alone(autocomplete_script):
+def test_completion_alone(autocomplete_script: PipTestEnvironment) -> None:
     """
     Test getting completion for none shell, just pip completion
     """
@@ -115,7 +146,7 @@ def test_completion_alone(autocomplete_script):
     )
 
 
-def test_completion_for_un_snippet(autocomplete):
+def test_completion_for_un_snippet(autocomplete: DoAutocomplete) -> None:
     """
     Test getting completion for ``un`` should return uninstall
     """
@@ -124,7 +155,7 @@ def test_completion_for_un_snippet(autocomplete):
     assert res.stdout.strip().split() == ["uninstall"], res.stdout
 
 
-def test_completion_for_default_parameters(autocomplete):
+def test_completion_for_default_parameters(autocomplete: DoAutocomplete) -> None:
     """
     Test getting completion for ``--`` should contain --help
     """
@@ -133,7 +164,7 @@ def test_completion_for_default_parameters(autocomplete):
     assert "--help" in res.stdout, "autocomplete function could not complete ``--``"
 
 
-def test_completion_option_for_command(autocomplete):
+def test_completion_option_for_command(autocomplete: DoAutocomplete) -> None:
     """
     Test getting completion for ``--`` in command (e.g. ``pip search --``)
     """
@@ -142,7 +173,7 @@ def test_completion_option_for_command(autocomplete):
     assert "--help" in res.stdout, "autocomplete function could not complete ``--``"
 
 
-def test_completion_short_option(autocomplete):
+def test_completion_short_option(autocomplete: DoAutocomplete) -> None:
     """
     Test getting completion for short options after ``-`` (eg. pip -)
     """
@@ -154,7 +185,7 @@ def test_completion_short_option(autocomplete):
     ), "autocomplete function could not complete short options after ``-``"
 
 
-def test_completion_short_option_for_command(autocomplete):
+def test_completion_short_option_for_command(autocomplete: DoAutocomplete) -> None:
     """
     Test getting completion for short options after ``-`` in command
     (eg. pip search -)
@@ -167,7 +198,9 @@ def test_completion_short_option_for_command(autocomplete):
     ), "autocomplete function could not complete short options after ``-``"
 
 
-def test_completion_files_after_option(autocomplete, data):
+def test_completion_files_after_option(
+    autocomplete: DoAutocomplete, data: TestData
+) -> None:
     """
     Test getting completion for <file> or <dir> after options in command
     (e.g. ``pip install -r``)
@@ -199,7 +232,9 @@ def test_completion_files_after_option(autocomplete, data):
     ), "autocomplete function could not complete <dir> after options in command"
 
 
-def test_completion_not_files_after_option(autocomplete, data):
+def test_completion_not_files_after_option(
+    autocomplete: DoAutocomplete, data: TestData
+) -> None:
     """
     Test not getting completion files after options which not applicable
     (e.g. ``pip install``)
@@ -222,7 +257,9 @@ def test_completion_not_files_after_option(autocomplete, data):
 
 
 @pytest.mark.parametrize("cl_opts", ["-U", "--user", "-h"])
-def test_completion_not_files_after_nonexpecting_option(autocomplete, data, cl_opts):
+def test_completion_not_files_after_nonexpecting_option(
+    autocomplete: DoAutocomplete, data: TestData, cl_opts: str
+) -> None:
     """
     Test not getting completion files after options which not applicable
     (e.g. ``pip install``)
@@ -244,7 +281,9 @@ def test_completion_not_files_after_nonexpecting_option(autocomplete, data, cl_o
     ), "autocomplete function completed <dir> when it should not complete"
 
 
-def test_completion_directories_after_option(autocomplete, data):
+def test_completion_directories_after_option(
+    autocomplete: DoAutocomplete, data: TestData
+) -> None:
     """
     Test getting completion <dir> after options in command
     (e.g. ``pip --cache-dir``)
@@ -267,7 +306,9 @@ def test_completion_directories_after_option(autocomplete, data):
         ), "autocomplete function could not complete <dir> after options"
 
 
-def test_completion_subdirectories_after_option(autocomplete, data):
+def test_completion_subdirectories_after_option(
+    autocomplete: DoAutocomplete, data: TestData
+) -> None:
     """
     Test getting completion <dir> after options in command
     given path of a directory
@@ -283,7 +324,9 @@ def test_completion_subdirectories_after_option(autocomplete, data):
     )
 
 
-def test_completion_path_after_option(autocomplete, data):
+def test_completion_path_after_option(
+    autocomplete: DoAutocomplete, data: TestData
+) -> None:
     """
     Test getting completion <path> after options in command
     given absolute path
@@ -303,8 +346,8 @@ def test_completion_path_after_option(autocomplete, data):
 
 @pytest.mark.parametrize("flag", ["--bash", "--zsh", "--fish"])
 def test_completion_uses_same_executable_name(
-    autocomplete_script, flag, deprecated_python
-):
+    autocomplete_script: PipTestEnvironment, flag: str, deprecated_python: bool
+) -> None:
     executable_name = "pip{}".format(sys.version_info[0])
     # Deprecated python versions produce an extra deprecation warning
     result = autocomplete_script.run(
diff --git a/tests/functional/test_configuration.py b/tests/functional/test_configuration.py
index a3047a45c93..9f656287507 100644
--- a/tests/functional/test_configuration.py
+++ b/tests/functional/test_configuration.py
@@ -1,21 +1,22 @@
 """Tests for the config command
 """
-
 import re
 import textwrap
 
 from pip._internal.cli.status_codes import ERROR
 from pip._internal.configuration import CONFIG_BASENAME, get_configuration_files
+from tests.lib import PipTestEnvironment
 from tests.lib.configuration_helpers import ConfigurationMixin, kinds
+from tests.lib.venv import VirtualEnvironment
 
 
-def test_no_options_passed_should_error(script):
+def test_no_options_passed_should_error(script: PipTestEnvironment) -> None:
     result = script.pip("config", expect_error=True)
     assert result.returncode == ERROR
 
 
 class TestBasicLoading(ConfigurationMixin):
-    def test_basic_modification_pipeline(self, script):
+    def test_basic_modification_pipeline(self, script: PipTestEnvironment) -> None:
         script.pip("config", "get", "test.blah", expect_error=True)
         script.pip("config", "set", "test.blah", "1")
 
@@ -25,7 +26,7 @@ def test_basic_modification_pipeline(self, script):
         script.pip("config", "unset", "test.blah")
         script.pip("config", "get", "test.blah", expect_error=True)
 
-    def test_listing_is_correct(self, script):
+    def test_listing_is_correct(self, script: PipTestEnvironment) -> None:
         script.pip("config", "set", "test.listing-beta", "2")
         script.pip("config", "set", "test.listing-alpha", "1")
         script.pip("config", "set", "test.listing-gamma", "3")
@@ -44,11 +45,11 @@ def test_listing_is_correct(self, script):
 
         assert lines == textwrap.dedent(expected).strip().splitlines()
 
-    def test_forget_section(self, script):
+    def test_forget_section(self, script: PipTestEnvironment) -> None:
         result = script.pip("config", "set", "isolated", "true", expect_error=True)
         assert "global.isolated" in result.stderr
 
-    def test_env_var_values(self, script):
+    def test_env_var_values(self, script: PipTestEnvironment) -> None:
         """Test that pip configuration set with environment variables
         is correctly displayed under "env_var".
         """
@@ -64,7 +65,7 @@ def test_env_var_values(self, script):
         assert "PIP_FIND_LINKS='http://mirror.example.com'" in result.stdout
         assert re.search(r"env_var:\n(  .+\n)+", result.stdout)
 
-    def test_env_values(self, script):
+    def test_env_values(self, script: PipTestEnvironment) -> None:
         """Test that custom pip configuration using the environment variable
         PIP_CONFIG_FILE is correctly displayed under "env". This configuration
         takes place of per-user configuration file displayed under "user".
@@ -90,10 +91,7 @@ def test_env_values(self, script):
         assert "freeze.timeout: 10" in result.stdout
         assert re.search(r"env:\n(  .+\n)+", result.stdout)
 
-    def test_user_values(
-        self,
-        script,
-    ):
+    def test_user_values(self, script: PipTestEnvironment) -> None:
         """Test that the user pip configuration set using --user
         is correctly displayed under "user".  This configuration takes place
         of custom path location using the environment variable PIP_CONFIG_FILE
@@ -112,7 +110,9 @@ def test_user_values(
         assert "freeze.timeout: 10" in result.stdout
         assert re.search(r"user:\n(  .+\n)+", result.stdout)
 
-    def test_site_values(self, script, virtualenv):
+    def test_site_values(
+        self, script: PipTestEnvironment, virtualenv: VirtualEnvironment
+    ) -> None:
         """Test that the current environment configuration set using --site
         is correctly displayed under "site".
         """
@@ -129,7 +129,7 @@ def test_site_values(self, script, virtualenv):
         assert "freeze.timeout: 10" in result.stdout
         assert re.search(r"site:\n(  .+\n)+", result.stdout)
 
-    def test_global_config_file(self, script):
+    def test_global_config_file(self, script: PipTestEnvironment) -> None:
         """Test that the system-wide  configuration can be identified"""
 
         # We cannot  write to system-wide files which might have permissions
diff --git a/tests/functional/test_debug.py b/tests/functional/test_debug.py
index f17490f96c0..41374f8cb88 100644
--- a/tests/functional/test_debug.py
+++ b/tests/functional/test_debug.py
@@ -1,7 +1,10 @@
+from typing import List
+
 import pytest
 
 from pip._internal.commands.debug import create_vendor_txt_map
 from pip._internal.utils import compatibility_tags
+from tests.lib import PipTestEnvironment
 
 
 @pytest.mark.parametrize(
@@ -21,7 +24,7 @@
         "vendored library versions:",
     ],
 )
-def test_debug(script, expected_text):
+def test_debug(script: PipTestEnvironment, expected_text: str) -> None:
     """
     Check that certain strings are present in the output.
     """
@@ -32,7 +35,7 @@ def test_debug(script, expected_text):
     assert expected_text in stdout
 
 
-def test_debug__library_versions(script):
+def test_debug__library_versions(script: PipTestEnvironment) -> None:
     """
     Check the library versions normal output.
     """
@@ -52,7 +55,7 @@ def test_debug__library_versions(script):
         ["--verbose"],
     ],
 )
-def test_debug__tags(script, args):
+def test_debug__tags(script: PipTestEnvironment, args: List[str]) -> None:
     """
     Check the compatible tag output.
     """
@@ -76,7 +79,9 @@ def test_debug__tags(script, args):
         (["--python-version", "3.7"], "(target: version_info='3.7')"),
     ],
 )
-def test_debug__target_options(script, args, expected):
+def test_debug__target_options(
+    script: PipTestEnvironment, args: List[str], expected: str
+) -> None:
     """
     Check passing target-related options.
     """
diff --git a/tests/functional/test_download.py b/tests/functional/test_download.py
index d41ec7f4954..c8d907cb0a4 100644
--- a/tests/functional/test_download.py
+++ b/tests/functional/test_download.py
@@ -2,17 +2,19 @@
 import shutil
 import textwrap
 from hashlib import sha256
+from typing import List
 
 import pytest
 
 from pip._internal.cli.status_codes import ERROR
 from pip._internal.utils.urls import path_to_url
-from tests.lib import create_really_basic_wheel
+from tests.conftest import MockServer, ScriptFactory
+from tests.lib import PipTestEnvironment, TestData, create_really_basic_wheel
 from tests.lib.path import Path
 from tests.lib.server import file_response
 
 
-def fake_wheel(data, wheel_path):
+def fake_wheel(data: TestData, wheel_path: str) -> None:
     wheel_name = os.path.basename(wheel_path)
     name, version, rest = wheel_name.split("-", 2)
     wheel_data = create_really_basic_wheel(name, version)
@@ -20,7 +22,7 @@ def fake_wheel(data, wheel_path):
 
 
 @pytest.mark.network
-def test_download_if_requested(script):
+def test_download_if_requested(script: PipTestEnvironment) -> None:
     """
     It should download (in the scratch path) and not install if requested.
     """
@@ -30,7 +32,7 @@ def test_download_if_requested(script):
 
 
 @pytest.mark.network
-def test_basic_download_setuptools(script):
+def test_basic_download_setuptools(script: PipTestEnvironment) -> None:
     """
     It should download (in the scratch path) and not install if requested.
     """
@@ -39,7 +41,7 @@ def test_basic_download_setuptools(script):
     assert any(path.startswith(setuptools_prefix) for path in result.files_created)
 
 
-def test_download_wheel(script, data):
+def test_download_wheel(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test using "pip download" to download a *.whl archive.
     """
@@ -51,7 +53,7 @@ def test_download_wheel(script, data):
 
 
 @pytest.mark.network
-def test_single_download_from_requirements_file(script):
+def test_single_download_from_requirements_file(script: PipTestEnvironment) -> None:
     """
     It should support download (in the scratch path) from PyPI from a
     requirements file
@@ -75,7 +77,9 @@ def test_single_download_from_requirements_file(script):
 
 
 @pytest.mark.network
-def test_basic_download_should_download_dependencies(script):
+def test_basic_download_should_download_dependencies(
+    script: PipTestEnvironment,
+) -> None:
     """
     It should download dependencies (in the scratch path)
     """
@@ -86,7 +90,7 @@ def test_basic_download_should_download_dependencies(script):
     result.did_not_create(script.site_packages / "openid")
 
 
-def test_download_wheel_archive(script, data):
+def test_download_wheel_archive(script: PipTestEnvironment, data: TestData) -> None:
     """
     It should download a wheel archive path
     """
@@ -96,7 +100,9 @@ def test_download_wheel_archive(script, data):
     result.did_create(Path("scratch") / wheel_filename)
 
 
-def test_download_should_download_wheel_deps(script, data):
+def test_download_should_download_wheel_deps(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     It should download dependencies for wheels(in the scratch path)
     """
@@ -111,7 +117,7 @@ def test_download_should_download_wheel_deps(script, data):
 
 
 @pytest.mark.network
-def test_download_should_skip_existing_files(script):
+def test_download_should_skip_existing_files(script: PipTestEnvironment) -> None:
     """
     It should not download files already existing in the scratch dir
     """
@@ -159,7 +165,7 @@ def test_download_should_skip_existing_files(script):
 
 
 @pytest.mark.network
-def test_download_vcs_link(script):
+def test_download_vcs_link(script: PipTestEnvironment) -> None:
     """
     It should allow -d flag for vcs links, regression test for issue #798.
     """
@@ -170,7 +176,9 @@ def test_download_vcs_link(script):
     result.did_not_create(script.site_packages / "piptestpackage")
 
 
-def test_only_binary_set_then_download_specific_platform(script, data):
+def test_only_binary_set_then_download_specific_platform(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Confirm that specifying an interpreter/platform constraint
     is allowed when ``--only-binary=:all:`` is set.
@@ -192,7 +200,9 @@ def test_only_binary_set_then_download_specific_platform(script, data):
     result.did_create(Path("scratch") / "fake-1.0-py2.py3-none-any.whl")
 
 
-def test_no_deps_set_then_download_specific_platform(script, data):
+def test_no_deps_set_then_download_specific_platform(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Confirm that specifying an interpreter/platform constraint
     is allowed when ``--no-deps`` is set.
@@ -214,7 +224,9 @@ def test_no_deps_set_then_download_specific_platform(script, data):
     result.did_create(Path("scratch") / "fake-1.0-py2.py3-none-any.whl")
 
 
-def test_download_specific_platform_fails(script, data):
+def test_download_specific_platform_fails(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Confirm that specifying an interpreter/platform constraint
     enforces that ``--no-deps`` or ``--only-binary=:all:`` is set.
@@ -236,7 +248,9 @@ def test_download_specific_platform_fails(script, data):
     assert "--only-binary=:all:" in result.stderr
 
 
-def test_no_binary_set_then_download_specific_platform_fails(script, data):
+def test_no_binary_set_then_download_specific_platform_fails(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Confirm that specifying an interpreter/platform constraint
     enforces that ``--only-binary=:all:`` is set without ``--no-binary``.
@@ -260,7 +274,7 @@ def test_no_binary_set_then_download_specific_platform_fails(script, data):
     assert "--only-binary=:all:" in result.stderr
 
 
-def test_download_specify_platform(script, data):
+def test_download_specify_platform(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test using "pip download --platform" to download a .whl archive
     supported for a specific platform
@@ -395,7 +409,9 @@ class TestDownloadPlatformManylinuxes:
             "manylinux2014_x86_64",
         ],
     )
-    def test_download_universal(self, platform, script, data):
+    def test_download_universal(
+        self, platform: str, script: PipTestEnvironment, data: TestData
+    ) -> None:
         """
         Universal wheels are returned even for specific platforms.
         """
@@ -427,11 +443,11 @@ def test_download_universal(self, platform, script, data):
     )
     def test_download_compatible_manylinuxes(
         self,
-        wheel_abi,
-        platform,
-        script,
-        data,
-    ):
+        wheel_abi: str,
+        platform: str,
+        script: PipTestEnvironment,
+        data: TestData,
+    ) -> None:
         """
         Earlier manylinuxes are compatible with later manylinuxes.
         """
@@ -451,7 +467,9 @@ def test_download_compatible_manylinuxes(
         )
         result.did_create(Path("scratch") / wheel)
 
-    def test_explicit_platform_only(self, data, script):
+    def test_explicit_platform_only(
+        self, data: TestData, script: PipTestEnvironment
+    ) -> None:
         """
         When specifying the platform, manylinux1 needs to be the
         explicit platform--it won't ever be added to the compatible
@@ -472,7 +490,7 @@ def test_explicit_platform_only(self, data, script):
         )
 
 
-def test_download__python_version(script, data):
+def test_download__python_version(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test using "pip download --python-version" to download a .whl archive
     supported for a specific interpreter
@@ -592,7 +610,9 @@ def test_download__python_version(script, data):
     result.did_create(Path("scratch") / "fake-2.0-py3-none-any.whl")
 
 
-def make_wheel_with_python_requires(script, package_name, python_requires):
+def make_wheel_with_python_requires(
+    script: PipTestEnvironment, package_name: str, python_requires: str
+) -> Path:
     """
     Create a wheel using the given python_requires.
 
@@ -623,7 +643,9 @@ def make_wheel_with_python_requires(script, package_name, python_requires):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_download__python_version_used_for_python_requires(script, data):
+def test_download__python_version_used_for_python_requires(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test that --python-version is used for the Requires-Python check.
     """
@@ -634,7 +656,7 @@ def test_download__python_version_used_for_python_requires(script, data):
     )
     wheel_dir = os.path.dirname(wheel_path)
 
-    def make_args(python_version):
+    def make_args(python_version: str) -> List[str]:
         return [
             "download",
             "--no-index",
@@ -662,7 +684,9 @@ def make_args(python_version):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_download_ignore_requires_python_dont_fail_with_wrong_python(script):
+def test_download_ignore_requires_python_dont_fail_with_wrong_python(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test that --ignore-requires-python ignores Requires-Python check.
     """
@@ -687,7 +711,7 @@ def test_download_ignore_requires_python_dont_fail_with_wrong_python(script):
     result.did_create(Path("scratch") / "mypackage-1.0-py2.py3-none-any.whl")
 
 
-def test_download_specify_abi(script, data):
+def test_download_specify_abi(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test using "pip download --abi" to download a .whl archive
     supported for a specific abi
@@ -804,7 +828,9 @@ def test_download_specify_abi(script, data):
     result.did_create(Path("scratch") / "fake-1.0-fk2-otherabi-fake_platform.whl")
 
 
-def test_download_specify_implementation(script, data):
+def test_download_specify_implementation(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test using "pip download --abi" to download a .whl archive
     supported for a specific abi
@@ -859,7 +885,9 @@ def test_download_specify_implementation(script, data):
     )
 
 
-def test_download_exit_status_code_when_no_requirements(script):
+def test_download_exit_status_code_when_no_requirements(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test download exit status code when no requirements specified
     """
@@ -868,7 +896,9 @@ def test_download_exit_status_code_when_no_requirements(script):
     assert result.returncode == ERROR
 
 
-def test_download_exit_status_code_when_blank_requirements_file(script):
+def test_download_exit_status_code_when_blank_requirements_file(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test download exit status code when blank requirements file specified
     """
@@ -876,7 +906,9 @@ def test_download_exit_status_code_when_blank_requirements_file(script):
     script.pip("download", "-r", "blank.txt")
 
 
-def test_download_prefer_binary_when_tarball_higher_than_wheel(script, data):
+def test_download_prefer_binary_when_tarball_higher_than_wheel(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     fake_wheel(data, "source-0.8-py2.py3-none-any.whl")
     result = script.pip(
         "download",
@@ -892,7 +924,9 @@ def test_download_prefer_binary_when_tarball_higher_than_wheel(script, data):
     result.did_not_create(Path("scratch") / "source-1.0.tar.gz")
 
 
-def test_prefer_binary_tarball_higher_than_wheel_req_file(script, data):
+def test_prefer_binary_tarball_higher_than_wheel_req_file(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     fake_wheel(data, "source-0.8-py2.py3-none-any.whl")
     script.scratch_path.joinpath("test-req.txt").write_text(
         textwrap.dedent(
@@ -917,7 +951,9 @@ def test_prefer_binary_tarball_higher_than_wheel_req_file(script, data):
     result.did_not_create(Path("scratch") / "source-1.0.tar.gz")
 
 
-def test_download_prefer_binary_when_wheel_doesnt_satisfy_req(script, data):
+def test_download_prefer_binary_when_wheel_doesnt_satisfy_req(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     fake_wheel(data, "source-0.8-py2.py3-none-any.whl")
     script.scratch_path.joinpath("test-req.txt").write_text(
         textwrap.dedent(
@@ -942,7 +978,9 @@ def test_download_prefer_binary_when_wheel_doesnt_satisfy_req(script, data):
     result.did_not_create(Path("scratch") / "source-0.8-py2.py3-none-any.whl")
 
 
-def test_prefer_binary_when_wheel_doesnt_satisfy_req_req_file(script, data):
+def test_prefer_binary_when_wheel_doesnt_satisfy_req_req_file(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     fake_wheel(data, "source-0.8-py2.py3-none-any.whl")
     script.scratch_path.joinpath("test-req.txt").write_text(
         textwrap.dedent(
@@ -967,7 +1005,9 @@ def test_prefer_binary_when_wheel_doesnt_satisfy_req_req_file(script, data):
     result.did_not_create(Path("scratch") / "source-0.8-py2.py3-none-any.whl")
 
 
-def test_download_prefer_binary_when_only_tarball_exists(script, data):
+def test_download_prefer_binary_when_only_tarball_exists(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     result = script.pip(
         "download",
         "--prefer-binary",
@@ -981,7 +1021,9 @@ def test_download_prefer_binary_when_only_tarball_exists(script, data):
     result.did_create(Path("scratch") / "source-1.0.tar.gz")
 
 
-def test_prefer_binary_when_only_tarball_exists_req_file(script, data):
+def test_prefer_binary_when_only_tarball_exists_req_file(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("test-req.txt").write_text(
         textwrap.dedent(
             """
@@ -1004,13 +1046,17 @@ def test_prefer_binary_when_only_tarball_exists_req_file(script, data):
 
 
 @pytest.fixture(scope="session")
-def shared_script(tmpdir_factory, script_factory):
+def shared_script(
+    tmpdir_factory: pytest.TempdirFactory, script_factory: ScriptFactory
+) -> PipTestEnvironment:
     tmpdir = Path(str(tmpdir_factory.mktemp("download_shared_script")))
     script = script_factory(tmpdir.joinpath("workspace"))
     return script
 
 
-def test_download_file_url(shared_script, shared_data, tmpdir):
+def test_download_file_url(
+    shared_script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     download_dir = tmpdir / "download"
     download_dir.mkdir()
     downloaded_path = download_dir / "simple-1.0.tar.gz"
@@ -1029,7 +1075,9 @@ def test_download_file_url(shared_script, shared_data, tmpdir):
     assert simple_pkg.read_bytes() == downloaded_path.read_bytes()
 
 
-def test_download_file_url_existing_ok_download(shared_script, shared_data, tmpdir):
+def test_download_file_url_existing_ok_download(
+    shared_script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     download_dir = tmpdir / "download"
     download_dir.mkdir()
     downloaded_path = download_dir / "simple-1.0.tar.gz"
@@ -1046,7 +1094,9 @@ def test_download_file_url_existing_ok_download(shared_script, shared_data, tmpd
     assert downloaded_path_bytes == downloaded_path.read_bytes()
 
 
-def test_download_file_url_existing_bad_download(shared_script, shared_data, tmpdir):
+def test_download_file_url_existing_bad_download(
+    shared_script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     download_dir = tmpdir / "download"
     download_dir.mkdir()
     downloaded_path = download_dir / "simple-1.0.tar.gz"
@@ -1063,7 +1113,12 @@ def test_download_file_url_existing_bad_download(shared_script, shared_data, tmp
     assert simple_pkg_bytes == downloaded_path.read_bytes()
 
 
-def test_download_http_url_bad_hash(shared_script, shared_data, tmpdir, mock_server):
+def test_download_http_url_bad_hash(
+    shared_script: PipTestEnvironment,
+    shared_data: TestData,
+    tmpdir: Path,
+    mock_server: MockServer,
+) -> None:
     """
     If already-downloaded file has bad checksum, re-download.
     """
@@ -1092,7 +1147,9 @@ def test_download_http_url_bad_hash(shared_script, shared_data, tmpdir, mock_ser
     assert requests[0]["HTTP_ACCEPT_ENCODING"] == "identity"
 
 
-def test_download_editable(script, data, tmpdir):
+def test_download_editable(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test 'pip download' of editables in requirement file.
     """
diff --git a/tests/functional/test_fast_deps.py b/tests/functional/test_fast_deps.py
index 202e1cd4216..b5dd1f2867a 100644
--- a/tests/functional/test_fast_deps.py
+++ b/tests/functional/test_fast_deps.py
@@ -1,12 +1,16 @@
 import fnmatch
 import json
+import pathlib
 from os.path import basename
+from typing import Iterable
 
 from pip._vendor.packaging.utils import canonicalize_name
 from pytest import mark
 
+from tests.lib import PipTestEnvironment, TestData, TestPipResult
 
-def pip(script, command, requirement):
+
+def pip(script: PipTestEnvironment, command: str, requirement: str) -> TestPipResult:
     return script.pip(
         command,
         "--prefer-binary",
@@ -17,7 +21,7 @@ def pip(script, command, requirement):
     )
 
 
-def assert_installed(script, names):
+def assert_installed(script: PipTestEnvironment, names: str) -> None:
     list_output = json.loads(script.pip("list", "--format=json").stdout)
     installed = {canonicalize_name(item["name"]) for item in list_output}
     assert installed.issuperset(map(canonicalize_name, names))
@@ -31,7 +35,9 @@ def assert_installed(script, names):
         ("Paste[flup]==3.4.2", ("Paste", "six", "flup")),
     ),
 )
-def test_install_from_pypi(requirement, expected, script):
+def test_install_from_pypi(
+    requirement: str, expected: str, script: PipTestEnvironment
+) -> None:
     pip(script, "install", requirement)
     assert_installed(script, expected)
 
@@ -44,23 +50,25 @@ def test_install_from_pypi(requirement, expected, script):
         ("Paste[flup]==3.4.2", ("Paste-3.4.2-*.whl", "six-*.whl", "flup-*")),
     ),
 )
-def test_download_from_pypi(requirement, expected, script):
+def test_download_from_pypi(
+    requirement: str, expected: Iterable[str], script: PipTestEnvironment
+) -> None:
     result = pip(script, "download", requirement)
-    created = list(map(basename, result.files_created))
+    created = [basename(f) for f in result.files_created]
     assert all(fnmatch.filter(created, f) for f in expected)
 
 
 @mark.network
-def test_build_wheel_with_deps(data, script):
+def test_build_wheel_with_deps(data: TestData, script: PipTestEnvironment) -> None:
     result = pip(script, "wheel", data.packages / "requiresPaste")
-    created = list(map(basename, result.files_created))
+    created = [basename(f) for f in result.files_created]
     assert fnmatch.filter(created, "requiresPaste-3.1.4-*.whl")
     assert fnmatch.filter(created, "Paste-3.4.2-*.whl")
     assert fnmatch.filter(created, "six-*.whl")
 
 
 @mark.network
-def test_require_hash(script, tmp_path):
+def test_require_hash(script: PipTestEnvironment, tmp_path: pathlib.Path) -> None:
     reqs = tmp_path / "requirements.txt"
     reqs.write_text(
         "idna==2.10"
@@ -76,12 +84,12 @@ def test_require_hash(script, tmp_path):
         str(reqs),
         allow_stderr_warning=True,
     )
-    created = list(map(basename, result.files_created))
+    created = [basename(f) for f in result.files_created]
     assert fnmatch.filter(created, "idna-2.10*")
 
 
 @mark.network
-def test_hash_mismatch(script, tmp_path):
+def test_hash_mismatch(script: PipTestEnvironment, tmp_path: pathlib.Path) -> None:
     reqs = tmp_path / "requirements.txt"
     reqs.write_text("idna==2.10 --hash=sha256:irna")
     result = script.pip(
diff --git a/tests/functional/test_freeze.py b/tests/functional/test_freeze.py
index 6756944ff43..bae9eadbd30 100644
--- a/tests/functional/test_freeze.py
+++ b/tests/functional/test_freeze.py
@@ -7,8 +7,10 @@
 import pytest
 from pip._vendor.packaging.utils import canonicalize_name
 
-from pip._internal.models.direct_url import DirectUrl
+from pip._internal.models.direct_url import DirectUrl, DirInfo
 from tests.lib import (
+    PipTestEnvironment,
+    TestData,
     _create_test_package,
     _create_test_package_with_srcdir,
     _git_commit,
@@ -21,11 +23,13 @@
     wheel,
 )
 from tests.lib.direct_url import get_created_direct_url_path
+from tests.lib.path import Path
+from tests.lib.venv import VirtualEnvironment
 
 distribute_re = re.compile("^distribute==[0-9.]+\n", re.MULTILINE)
 
 
-def _check_output(result, expected):
+def _check_output(result: str, expected: str) -> None:
     checker = OutputChecker()
     actual = str(result)
 
@@ -44,7 +48,7 @@ def _check_output(result, expected):
     # with distribute installed.
     actual = distribute_re.sub("", actual)
 
-    def banner(msg):
+    def banner(msg: str) -> str:
         return f"\n========== {msg} ==========\n"
 
     assert checker.check_output(expected, actual, ELLIPSIS), (
@@ -52,7 +56,7 @@ def banner(msg):
     )
 
 
-def test_basic_freeze(script):
+def test_basic_freeze(script: PipTestEnvironment) -> None:
     """
     Some tests of freeze, first we have to install some stuff.  Note that
     the test is a little crude at the end because Python 2.5+ adds egg
@@ -84,13 +88,13 @@ def test_basic_freeze(script):
     _check_output(result.stdout, expected)
 
 
-def test_freeze_with_pip(script):
+def test_freeze_with_pip(script: PipTestEnvironment) -> None:
     """Test pip shows itself"""
     result = script.pip("freeze", "--all")
     assert "pip==" in result.stdout
 
 
-def test_exclude_and_normalization(script, tmpdir):
+def test_exclude_and_normalization(script: PipTestEnvironment, tmpdir: Path) -> None:
     req_path = wheel.make_wheel(name="Normalizable_Name", version="1.0").save_to_dir(
         tmpdir
     )
@@ -102,7 +106,7 @@ def test_exclude_and_normalization(script, tmpdir):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_freeze_multiple_exclude_with_all(script):
+def test_freeze_multiple_exclude_with_all(script: PipTestEnvironment) -> None:
     result = script.pip("freeze", "--all")
     assert "pip==" in result.stdout
     assert "wheel==" in result.stdout
@@ -111,12 +115,12 @@ def test_freeze_multiple_exclude_with_all(script):
     assert "wheel==" not in result.stdout
 
 
-def test_freeze_with_invalid_names(script):
+def test_freeze_with_invalid_names(script: PipTestEnvironment) -> None:
     """
     Test that invalid names produce warnings and are passed over gracefully.
     """
 
-    def fake_install(pkgname, dest):
+    def fake_install(pkgname: str, dest: str) -> None:
         egg_info_path = os.path.join(
             dest,
             "{}-1.0-py{}.{}.egg-info".format(
@@ -167,7 +171,7 @@ def fake_install(pkgname, dest):
 
 
 @pytest.mark.git
-def test_freeze_editable_not_vcs(script):
+def test_freeze_editable_not_vcs(script: PipTestEnvironment) -> None:
     """
     Test an editable install that is not version controlled.
     """
@@ -192,7 +196,9 @@ def test_freeze_editable_not_vcs(script):
 
 
 @pytest.mark.git
-def test_freeze_editable_git_with_no_remote(script, deprecated_python):
+def test_freeze_editable_git_with_no_remote(
+    script: PipTestEnvironment, deprecated_python: bool
+) -> None:
     """
     Test an editable Git install with no remote url.
     """
@@ -217,7 +223,7 @@ def test_freeze_editable_git_with_no_remote(script, deprecated_python):
 
 
 @need_svn
-def test_freeze_svn(script):
+def test_freeze_svn(script: PipTestEnvironment) -> None:
     """Test freezing a svn checkout"""
 
     checkout_path = _create_test_package(script, vcs="svn")
@@ -240,7 +246,7 @@ def test_freeze_svn(script):
     run=True,
     strict=True,
 )
-def test_freeze_exclude_editable(script):
+def test_freeze_exclude_editable(script: PipTestEnvironment) -> None:
     """
     Test excluding editable from freezing list.
     """
@@ -273,7 +279,7 @@ def test_freeze_exclude_editable(script):
 
 
 @pytest.mark.git
-def test_freeze_git_clone(script):
+def test_freeze_git_clone(script: PipTestEnvironment) -> None:
     """
     Test freezing a Git clone.
     """
@@ -331,7 +337,7 @@ def test_freeze_git_clone(script):
 
 
 @pytest.mark.git
-def test_freeze_git_clone_srcdir(script):
+def test_freeze_git_clone_srcdir(script: PipTestEnvironment) -> None:
     """
     Test freezing a Git clone where setup.py is in a subdirectory
     relative the repo root and the source code is in a subdirectory
@@ -366,7 +372,7 @@ def test_freeze_git_clone_srcdir(script):
 
 
 @need_mercurial
-def test_freeze_mercurial_clone_srcdir(script):
+def test_freeze_mercurial_clone_srcdir(script: PipTestEnvironment) -> None:
     """
     Test freezing a Mercurial clone where setup.py is in a subdirectory
     relative to the repo root and the source code is in a subdirectory
@@ -389,7 +395,7 @@ def test_freeze_mercurial_clone_srcdir(script):
 
 
 @pytest.mark.git
-def test_freeze_git_remote(script):
+def test_freeze_git_remote(script: PipTestEnvironment) -> None:
     """
     Test freezing a Git clone.
     """
@@ -472,7 +478,7 @@ def test_freeze_git_remote(script):
 
 
 @need_mercurial
-def test_freeze_mercurial_clone(script):
+def test_freeze_mercurial_clone(script: PipTestEnvironment) -> None:
     """
     Test freezing a Mercurial clone.
 
@@ -506,7 +512,7 @@ def test_freeze_mercurial_clone(script):
 
 
 @need_bzr
-def test_freeze_bazaar_clone(script):
+def test_freeze_bazaar_clone(script: PipTestEnvironment) -> None:
     """
     Test freezing a Bazaar clone.
 
@@ -539,7 +545,9 @@ def test_freeze_bazaar_clone(script):
     "outer_vcs, inner_vcs",
     [("hg", "git"), ("git", "hg")],
 )
-def test_freeze_nested_vcs(script, outer_vcs, inner_vcs):
+def test_freeze_nested_vcs(
+    script: PipTestEnvironment, outer_vcs: str, inner_vcs: str
+) -> None:
     """Test VCS can be correctly freezed when resides inside another VCS repo."""
     # Create Python package.
     pkg_path = _create_test_package(script, vcs=inner_vcs)
@@ -585,8 +593,8 @@ def test_freeze_nested_vcs(script, outer_vcs, inner_vcs):
 
 
 def test_freeze_with_requirement_option_file_url_egg_not_installed(
-    script, deprecated_python
-):
+    script: PipTestEnvironment, deprecated_python: bool
+) -> None:
     """
     Test "freeze -r requirements.txt" with a local file URL whose egg name
     is not installed.
@@ -612,7 +620,7 @@ def test_freeze_with_requirement_option_file_url_egg_not_installed(
         assert expected_err == result.stderr
 
 
-def test_freeze_with_requirement_option(script):
+def test_freeze_with_requirement_option(script: PipTestEnvironment) -> None:
     """
     Test that new requirements are created correctly with --requirement hints
 
@@ -672,7 +680,7 @@ def test_freeze_with_requirement_option(script):
     ) in result.stderr
 
 
-def test_freeze_with_requirement_option_multiple(script):
+def test_freeze_with_requirement_option_multiple(script: PipTestEnvironment) -> None:
     """
     Test that new requirements are created correctly with multiple
     --requirement hints
@@ -741,7 +749,9 @@ def test_freeze_with_requirement_option_multiple(script):
     assert result.stdout.count("--index-url http://ignore") == 1
 
 
-def test_freeze_with_requirement_option_package_repeated_one_file(script):
+def test_freeze_with_requirement_option_package_repeated_one_file(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test freezing with single requirements file that contains a package
     multiple times
@@ -788,7 +798,9 @@ def test_freeze_with_requirement_option_package_repeated_one_file(script):
     assert result.stderr.count("is not installed") == 1
 
 
-def test_freeze_with_requirement_option_package_repeated_multi_file(script):
+def test_freeze_with_requirement_option_package_repeated_multi_file(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test freezing with multiple requirements file that contain a package
     """
@@ -846,7 +858,9 @@ def test_freeze_with_requirement_option_package_repeated_multi_file(script):
 
 @pytest.mark.network
 @pytest.mark.incompatible_with_test_venv
-def test_freeze_user(script, virtualenv, data):
+def test_freeze_user(
+    script: PipTestEnvironment, virtualenv: VirtualEnvironment, data: TestData
+) -> None:
     """
     Testing freeze with --user, first we have to install some stuff.
     """
@@ -864,7 +878,7 @@ def test_freeze_user(script, virtualenv, data):
 
 
 @pytest.mark.network
-def test_freeze_path(tmpdir, script, data):
+def test_freeze_path(tmpdir: Path, script: PipTestEnvironment, data: TestData) -> None:
     """
     Test freeze with --path.
     """
@@ -882,7 +896,9 @@ def test_freeze_path(tmpdir, script, data):
 
 @pytest.mark.network
 @pytest.mark.incompatible_with_test_venv
-def test_freeze_path_exclude_user(tmpdir, script, data):
+def test_freeze_path_exclude_user(
+    tmpdir: Path, script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test freeze with --path and make sure packages from --user are not picked
     up.
@@ -908,7 +924,9 @@ def test_freeze_path_exclude_user(tmpdir, script, data):
 
 
 @pytest.mark.network
-def test_freeze_path_multiple(tmpdir, script, data):
+def test_freeze_path_multiple(
+    tmpdir: Path, script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test freeze with multiple --path arguments.
     """
@@ -940,7 +958,9 @@ def test_freeze_path_multiple(tmpdir, script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_freeze_direct_url_archive(script, shared_data):
+def test_freeze_direct_url_archive(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
     req = "simple @ " + path_to_url(shared_data.packages / "simple-2.0.tar.gz")
     assert req.startswith("simple @ file://")
     script.pip("install", req)
@@ -948,7 +968,7 @@ def test_freeze_direct_url_archive(script, shared_data):
     assert req in result.stdout
 
 
-def test_freeze_skip_work_dir_pkg(script):
+def test_freeze_skip_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that freeze should not include package
     present in working directory
@@ -963,7 +983,7 @@ def test_freeze_skip_work_dir_pkg(script):
     assert "simple" not in result.stdout
 
 
-def test_freeze_include_work_dir_pkg(script):
+def test_freeze_include_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that freeze should include package in working directory
     if working directory is added in PYTHONPATH
@@ -981,7 +1001,8 @@ def test_freeze_include_work_dir_pkg(script):
     assert "simple==1.0" in result.stdout
 
 
-def test_freeze_pep610_editable(script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_freeze_pep610_editable(script: PipTestEnvironment) -> None:
     """
     Test that a package installed with a direct_url.json with editable=true
     is correctly frozeon as editable.
@@ -993,6 +1014,7 @@ def test_freeze_pep610_editable(script, with_wheel):
     # patch direct_url.json to simulate an editable install
     with open(direct_url_path) as f:
         direct_url = DirectUrl.from_json(f.read())
+    assert isinstance(direct_url.info, DirInfo)
     direct_url.info.editable = True
     with open(direct_url_path, "w") as f:
         f.write(direct_url.to_json())
diff --git a/tests/functional/test_hash.py b/tests/functional/test_hash.py
index f6dd8b2a3d5..7734ce58bb1 100644
--- a/tests/functional/test_hash.py
+++ b/tests/functional/test_hash.py
@@ -1,7 +1,9 @@
 """Tests for the ``pip hash`` command"""
+from tests.lib import PipTestEnvironment
+from tests.lib.path import Path
 
 
-def test_basic_hash(script, tmpdir):
+def test_basic_hash(script: PipTestEnvironment, tmpdir: Path) -> None:
     """Run 'pip hash' through its default behavior."""
     expected = (
         "--hash=sha256:2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425"
@@ -11,7 +13,7 @@ def test_basic_hash(script, tmpdir):
     assert expected in str(result)
 
 
-def test_good_algo_option(script, tmpdir):
+def test_good_algo_option(script: PipTestEnvironment, tmpdir: Path) -> None:
     """Make sure the -a option works."""
     expected = (
         "--hash=sha512:9b71d224bd62f3785d96d46ad3ea3d73319bfbc2890caad"
@@ -22,7 +24,7 @@ def test_good_algo_option(script, tmpdir):
     assert expected in str(result)
 
 
-def test_bad_algo_option(script, tmpdir):
+def test_bad_algo_option(script: PipTestEnvironment, tmpdir: Path) -> None:
     """Make sure the -a option raises an error when given a bad operand."""
     result = script.pip(
         "hash", "-a", "invalidname", _hello_file(tmpdir), expect_error=True
@@ -30,7 +32,7 @@ def test_bad_algo_option(script, tmpdir):
     assert "invalid choice: 'invalidname'" in str(result)
 
 
-def _hello_file(tmpdir):
+def _hello_file(tmpdir: Path) -> Path:
     """Return a temp file to hash containing "hello"."""
     file = tmpdir / "hashable"
     file.write_text("hello")
diff --git a/tests/functional/test_help.py b/tests/functional/test_help.py
index e50a9326289..dba41af5f79 100644
--- a/tests/functional/test_help.py
+++ b/tests/functional/test_help.py
@@ -5,43 +5,46 @@
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.commands import commands_dict, create_command
 from pip._internal.exceptions import CommandError
+from tests.conftest import InMemoryPip
+from tests.lib import PipTestEnvironment
 
 
-def test_run_method_should_return_success_when_finds_command_name():
+def test_run_method_should_return_success_when_finds_command_name() -> None:
     """
     Test HelpCommand.run for existing command
     """
     options_mock = Mock()
-    args = ("freeze",)
+    args = ["freeze"]
     help_cmd = create_command("help")
     status = help_cmd.run(options_mock, args)
     assert status == SUCCESS
 
 
-def test_run_method_should_return_success_when_command_name_not_specified():
+def test_run_method_should_return_success_when_command_name_not_specified() -> None:
     """
     Test HelpCommand.run when there are no args
     """
     options_mock = Mock()
-    args = ()
     help_cmd = create_command("help")
-    status = help_cmd.run(options_mock, args)
+    status = help_cmd.run(options_mock, [])
     assert status == SUCCESS
 
 
-def test_run_method_should_raise_command_error_when_command_does_not_exist():
+def test_run_method_should_raise_command_error_when_command_does_not_exist() -> None:
     """
     Test HelpCommand.run for non-existing command
     """
     options_mock = Mock()
-    args = ("mycommand",)
+    args = ["mycommand"]
     help_cmd = create_command("help")
 
     with pytest.raises(CommandError):
         help_cmd.run(options_mock, args)
 
 
-def test_help_command_should_exit_status_ok_when_command_exists(script):
+def test_help_command_should_exit_status_ok_when_command_exists(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test `help` command for existing command
     """
@@ -49,7 +52,9 @@ def test_help_command_should_exit_status_ok_when_command_exists(script):
     assert result.returncode == SUCCESS
 
 
-def test_help_command_should_exit_status_ok_when_no_cmd_is_specified(script):
+def test_help_command_should_exit_status_ok_when_no_cmd_is_specified(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test `help` command for no command
     """
@@ -57,7 +62,9 @@ def test_help_command_should_exit_status_ok_when_no_cmd_is_specified(script):
     assert result.returncode == SUCCESS
 
 
-def test_help_command_should_exit_status_error_when_cmd_does_not_exist(script):
+def test_help_command_should_exit_status_error_when_cmd_does_not_exist(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test `help` command for non-existing command
     """
@@ -65,7 +72,7 @@ def test_help_command_should_exit_status_error_when_cmd_does_not_exist(script):
     assert result.returncode == ERROR
 
 
-def test_help_command_redact_auth_from_url(script):
+def test_help_command_redact_auth_from_url(script: PipTestEnvironment) -> None:
     """
     Test `help` on various subcommands redact auth from url
     """
@@ -75,7 +82,9 @@ def test_help_command_redact_auth_from_url(script):
     assert "secret" not in result.stdout
 
 
-def test_help_command_redact_auth_from_url_with_extra_index_url(script):
+def test_help_command_redact_auth_from_url_with_extra_index_url(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test `help` on various subcommands redact auth from url with extra index url
     """
@@ -86,7 +95,7 @@ def test_help_command_redact_auth_from_url_with_extra_index_url(script):
     assert "secret" not in result.stdout
 
 
-def test_help_commands_equally_functional(in_memory_pip):
+def test_help_commands_equally_functional(in_memory_pip: InMemoryPip) -> None:
     """
     Test if `pip help` and 'pip --help' behave the same way.
     """
diff --git a/tests/functional/test_index.py b/tests/functional/test_index.py
index a7f1a8817e2..43b8f09c311 100644
--- a/tests/functional/test_index.py
+++ b/tests/functional/test_index.py
@@ -2,10 +2,11 @@
 
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.commands import create_command
+from tests.lib import PipTestEnvironment
 
 
 @pytest.mark.network
-def test_list_all_versions_basic_search(script):
+def test_list_all_versions_basic_search(script: PipTestEnvironment) -> None:
     """
     End to end test of index versions command.
     """
@@ -27,7 +28,7 @@ def test_list_all_versions_basic_search(script):
 
 
 @pytest.mark.network
-def test_list_all_versions_search_with_pre(script):
+def test_list_all_versions_search_with_pre(script: PipTestEnvironment) -> None:
     """
     See that adding the --pre flag adds pre-releases
     """
@@ -49,7 +50,7 @@ def test_list_all_versions_search_with_pre(script):
 
 
 @pytest.mark.network
-def test_list_all_versions_returns_no_matches_found_when_name_not_exact():
+def test_list_all_versions_returns_no_matches_found_when_name_not_exact() -> None:
     """
     Test that non exact name do not match
     """
@@ -62,7 +63,7 @@ def test_list_all_versions_returns_no_matches_found_when_name_not_exact():
 
 
 @pytest.mark.network
-def test_list_all_versions_returns_matches_found_when_name_is_exact():
+def test_list_all_versions_returns_matches_found_when_name_is_exact() -> None:
     """
     Test that exact name matches
     """
diff --git a/tests/functional/test_install.py b/tests/functional/test_install.py
index a0b92be223f..a18c49c4521 100644
--- a/tests/functional/test_install.py
+++ b/tests/functional/test_install.py
@@ -7,13 +7,18 @@
 import sys
 import textwrap
 from os.path import curdir, join, pardir
+from typing import Dict, List, Tuple
 
 import pytest
 
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.models.index import PyPI, TestPyPI
 from pip._internal.utils.misc import rmtree
+from tests.conftest import CertFactory
 from tests.lib import (
+    PipTestEnvironment,
+    ResolverVariant,
+    TestData,
     _create_svn_repo,
     _create_test_package,
     create_basic_wheel_for_package,
@@ -38,7 +43,13 @@
 
 @pytest.mark.parametrize("command", ("install", "wheel"))
 @pytest.mark.parametrize("variant", ("missing_setuptools", "bad_setuptools"))
-def test_pep518_uses_build_env(script, data, common_wheels, command, variant):
+def test_pep518_uses_build_env(
+    script: PipTestEnvironment,
+    data: TestData,
+    common_wheels: Path,
+    command: str,
+    variant: str,
+) -> None:
     if variant == "missing_setuptools":
         script.pip("uninstall", "-y", "setuptools")
     elif variant == "bad_setuptools":
@@ -59,8 +70,12 @@ def test_pep518_uses_build_env(script, data, common_wheels, command, variant):
 
 
 def test_pep518_build_env_uses_same_pip(
-    script, data, pip_src, common_wheels, deprecated_python
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    pip_src: Path,
+    common_wheels: Path,
+    deprecated_python: bool,
+) -> None:
     """Ensure the subprocess call to pip for installing the
     build dependencies is using the same version of pip.
     """
@@ -80,7 +95,9 @@ def test_pep518_build_env_uses_same_pip(
     )
 
 
-def test_pep518_refuses_conflicting_requires(script, data):
+def test_pep518_refuses_conflicting_requires(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     create_basic_wheel_for_package(script, "setuptools", "1.0")
     create_basic_wheel_for_package(script, "wheel", "1.0")
     project_dir = data.src.joinpath("pep518_conflicting_requires")
@@ -99,7 +116,9 @@ def test_pep518_refuses_conflicting_requires(script, data):
     ), str(result)
 
 
-def test_pep518_refuses_invalid_requires(script, data, common_wheels):
+def test_pep518_refuses_invalid_requires(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     result = script.pip(
         "install",
         "-f",
@@ -116,7 +135,9 @@ def test_pep518_refuses_invalid_requires(script, data, common_wheels):
     assert "pyproject.toml" in result.stderr
 
 
-def test_pep518_refuses_invalid_build_system(script, data, common_wheels):
+def test_pep518_refuses_invalid_build_system(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     result = script.pip(
         "install",
         "-f",
@@ -133,7 +154,9 @@ def test_pep518_refuses_invalid_build_system(script, data, common_wheels):
     assert "pyproject.toml" in result.stderr
 
 
-def test_pep518_allows_missing_requires(script, data, common_wheels):
+def test_pep518_allows_missing_requires(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     result = script.pip(
         "install",
         "-f",
@@ -152,7 +175,9 @@ def test_pep518_allows_missing_requires(script, data, common_wheels):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_pep518_with_user_pip(script, pip_src, data, common_wheels):
+def test_pep518_with_user_pip(
+    script: PipTestEnvironment, pip_src: Path, data: TestData, common_wheels: Path
+) -> None:
     """
     Check that build dependencies are installed into the build
     environment without using build isolation for the pip invocation.
@@ -179,7 +204,9 @@ def test_pep518_with_user_pip(script, pip_src, data, common_wheels):
     )
 
 
-def test_pep518_with_extra_and_markers(script, data, common_wheels):
+def test_pep518_with_extra_and_markers(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     script.pip(
         "wheel",
         "--no-index",
@@ -191,7 +218,9 @@ def test_pep518_with_extra_and_markers(script, data, common_wheels):
     )
 
 
-def test_pep518_with_namespace_package(script, data, common_wheels):
+def test_pep518_with_namespace_package(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     script.pip(
         "wheel",
         "--no-index",
@@ -209,7 +238,13 @@ def test_pep518_with_namespace_package(script, data, common_wheels):
     "package",
     ("pep518_forkbomb", "pep518_twin_forkbombs_first", "pep518_twin_forkbombs_second"),
 )
-def test_pep518_forkbombs(script, data, common_wheels, command, package):
+def test_pep518_forkbombs(
+    script: PipTestEnvironment,
+    data: TestData,
+    common_wheels: Path,
+    command: str,
+    package: str,
+) -> None:
     package_source = next(data.packages.glob(package + "-[0-9]*.tar.gz"))
     result = script.pip(
         command,
@@ -234,8 +269,12 @@ def test_pep518_forkbombs(script, data, common_wheels, command, package):
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
 def test_pip_second_command_line_interface_works(
-    script, pip_src, data, common_wheels, deprecated_python
-):
+    script: PipTestEnvironment,
+    pip_src: Path,
+    data: TestData,
+    common_wheels: Path,
+    deprecated_python: bool,
+) -> None:
     """
     Check if ``pip<PYVERSION>`` commands behaves equally
     """
@@ -251,7 +290,9 @@ def test_pip_second_command_line_interface_works(
     result.did_create(initools_folder)
 
 
-def test_install_exit_status_code_when_no_requirements(script):
+def test_install_exit_status_code_when_no_requirements(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test install exit status code when no requirements specified
     """
@@ -260,7 +301,9 @@ def test_install_exit_status_code_when_no_requirements(script):
     assert result.returncode == ERROR
 
 
-def test_install_exit_status_code_when_blank_requirements_file(script):
+def test_install_exit_status_code_when_blank_requirements_file(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test install exit status code when blank requirements file specified
     """
@@ -270,7 +313,7 @@ def test_install_exit_status_code_when_blank_requirements_file(script):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_basic_install_from_pypi(script):
+def test_basic_install_from_pypi(script: PipTestEnvironment) -> None:
     """
     Test installing a package from PyPI.
     """
@@ -292,7 +335,7 @@ def test_basic_install_from_pypi(script):
     assert "https://" not in result.stdout
 
 
-def test_basic_editable_install(script):
+def test_basic_editable_install(script: PipTestEnvironment) -> None:
     """
     Test editable installation.
     """
@@ -302,7 +345,7 @@ def test_basic_editable_install(script):
 
 
 @need_svn
-def test_basic_install_editable_from_svn(script):
+def test_basic_install_editable_from_svn(script: PipTestEnvironment) -> None:
     """
     Test checking out from svn.
     """
@@ -312,7 +355,7 @@ def test_basic_install_editable_from_svn(script):
     result.assert_installed("version-pkg", with_files=[".svn"])
 
 
-def _test_install_editable_from_git(script):
+def _test_install_editable_from_git(script: PipTestEnvironment) -> None:
     """Test cloning from Git."""
     pkg_path = _create_test_package(script, name="testpackage", vcs="git")
     args = [
@@ -324,17 +367,19 @@ def _test_install_editable_from_git(script):
     result.assert_installed("testpackage", with_files=[".git"])
 
 
-def test_basic_install_editable_from_git(script):
+def test_basic_install_editable_from_git(script: PipTestEnvironment) -> None:
     _test_install_editable_from_git(script)
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_editable_from_git_autobuild_wheel(script):
+def test_install_editable_from_git_autobuild_wheel(script: PipTestEnvironment) -> None:
     _test_install_editable_from_git(script)
 
 
 @pytest.mark.network
-def test_install_editable_uninstalls_existing(data, script, tmpdir):
+def test_install_editable_uninstalls_existing(
+    data: TestData, script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test that installing an editable uninstalls a previously installed
     non-editable version.
@@ -362,7 +407,9 @@ def test_install_editable_uninstalls_existing(data, script, tmpdir):
     assert "Successfully uninstalled pip-test-package" in result.stdout
 
 
-def test_install_editable_uninstalls_existing_from_path(script, data):
+def test_install_editable_uninstalls_existing_from_path(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test that installing an editable uninstalls a previously installed
     non-editable version from path
@@ -388,7 +435,7 @@ def test_install_editable_uninstalls_existing_from_path(script, data):
 
 
 @need_mercurial
-def test_basic_install_editable_from_hg(script):
+def test_basic_install_editable_from_hg(script: PipTestEnvironment) -> None:
     """Test cloning and hg+file install from Mercurial."""
     pkg_path = _create_test_package(script, name="testpackage", vcs="hg")
     url = "hg+{}#egg=testpackage".format(path_to_url(pkg_path))
@@ -399,7 +446,7 @@ def test_basic_install_editable_from_hg(script):
 
 
 @need_mercurial
-def test_vcs_url_final_slash_normalization(script):
+def test_vcs_url_final_slash_normalization(script: PipTestEnvironment) -> None:
     """
     Test that presence or absence of final slash in VCS URL is normalized.
     """
@@ -414,7 +461,7 @@ def test_vcs_url_final_slash_normalization(script):
 
 
 @need_bzr
-def test_install_editable_from_bazaar(script):
+def test_install_editable_from_bazaar(script: PipTestEnvironment) -> None:
     """Test checking out from Bazaar."""
     pkg_path = _create_test_package(script, name="testpackage", vcs="bazaar")
     args = [
@@ -428,7 +475,9 @@ def test_install_editable_from_bazaar(script):
 
 @pytest.mark.network
 @need_bzr
-def test_vcs_url_urlquote_normalization(script, tmpdir):
+def test_vcs_url_urlquote_normalization(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test that urlquoted characters are normalized for repo URL comparison.
     """
@@ -448,7 +497,9 @@ def test_vcs_url_urlquote_normalization(script, tmpdir):
 
 @pytest.mark.parametrize("resolver", ["", "--use-deprecated=legacy-resolver"])
 @pytest.mark.usefixtures("with_wheel")
-def test_basic_install_from_local_directory(script, data, resolver):
+def test_basic_install_from_local_directory(
+    script: PipTestEnvironment, data: TestData, resolver: str
+) -> None:
     """
     Test installing from a local directory.
     """
@@ -476,7 +527,9 @@ def test_basic_install_from_local_directory(script, data, resolver):
     ],
 )
 @pytest.mark.usefixtures("with_wheel")
-def test_basic_install_relative_directory(script, data, test_type, editable):
+def test_basic_install_relative_directory(
+    script: PipTestEnvironment, data: TestData, test_type: str, editable: bool
+) -> None:
     """
     Test installing a requirement using a relative path.
     """
@@ -508,7 +561,7 @@ def test_basic_install_relative_directory(script, data, test_type, editable):
         result.did_create(egg_link_file)
 
 
-def test_install_quiet(script, data):
+def test_install_quiet(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test that install -q is actually quiet.
     """
@@ -522,7 +575,9 @@ def test_install_quiet(script, data):
     assert result.stderr == ""
 
 
-def test_hashed_install_success(script, data, tmpdir):
+def test_hashed_install_success(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test that installing various sorts of requirements with correct hashes
     works.
@@ -542,7 +597,7 @@ def test_hashed_install_success(script, data, tmpdir):
         script.pip_install_local("-r", reqs_file.resolve())
 
 
-def test_hashed_install_failure(script, tmpdir):
+def test_hashed_install_failure(script: PipTestEnvironment, tmpdir: Path) -> None:
     """Test that wrong hashes stop installation.
 
     This makes sure prepare_files() is called in the course of installation
@@ -559,13 +614,15 @@ def test_hashed_install_failure(script, tmpdir):
     assert len(result.files_created) == 0
 
 
-def assert_re_match(pattern, text):
+def assert_re_match(pattern: str, text: str) -> None:
     assert re.search(pattern, text), f"Could not find {pattern!r} in {text!r}"
 
 
 @pytest.mark.network
 @pytest.mark.skip("Fails on new resolver")
-def test_hashed_install_failure_later_flag(script, tmpdir):
+def test_hashed_install_failure_later_flag(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     with requirements_file(
         "blessings==1.0\n"
         "tracefront==0.1 --hash=sha256:somehash\n"
@@ -592,7 +649,9 @@ def test_hashed_install_failure_later_flag(script, tmpdir):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_from_local_directory_with_symlinks_to_directories(script, data):
+def test_install_from_local_directory_with_symlinks_to_directories(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing from a local directory containing symlinks to directories.
     """
@@ -610,7 +669,9 @@ def test_install_from_local_directory_with_symlinks_to_directories(script, data)
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_from_local_directory_with_in_tree_build(script, data):
+def test_install_from_local_directory_with_in_tree_build(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing from a local directory with default in tree build.
     """
@@ -629,7 +690,9 @@ def test_install_from_local_directory_with_in_tree_build(script, data):
 
 @pytest.mark.skipif("sys.platform == 'win32'")
 @pytest.mark.usefixtures("with_wheel")
-def test_install_from_local_directory_with_socket_file(script, data, tmpdir):
+def test_install_from_local_directory_with_socket_file(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing from a local directory containing a socket file.
     """
@@ -657,7 +720,9 @@ def test_install_from_local_directory_with_socket_file(script, data, tmpdir):
     assert str(socket_file_path) in result.stderr
 
 
-def test_install_from_local_directory_with_no_setup_py(script, data):
+def test_install_from_local_directory_with_no_setup_py(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing from a local directory with no 'setup.py'.
     """
@@ -666,7 +731,9 @@ def test_install_from_local_directory_with_no_setup_py(script, data):
     assert "Neither 'setup.py' nor 'pyproject.toml' found." in result.stderr
 
 
-def test_editable_install__local_dir_no_setup_py(script, data):
+def test_editable_install__local_dir_no_setup_py(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing in editable mode from a local directory with no setup.py.
     """
@@ -678,7 +745,9 @@ def test_editable_install__local_dir_no_setup_py(script, data):
     )
 
 
-def test_editable_install__local_dir_no_setup_py_with_pyproject(script):
+def test_editable_install__local_dir_no_setup_py_with_pyproject(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test installing in editable mode from a local directory with no setup.py
     but that does have pyproject.toml.
@@ -697,7 +766,9 @@ def test_editable_install__local_dir_no_setup_py_with_pyproject(script):
     assert "cannot be installed in editable mode" in msg
 
 
-def test_editable_install__local_dir_setup_requires_with_pyproject(script, shared_data):
+def test_editable_install__local_dir_setup_requires_with_pyproject(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
     """
     Test installing in editable mode from a local directory with a setup.py
     that has setup_requires and a pyproject.toml.
@@ -718,7 +789,7 @@ def test_editable_install__local_dir_setup_requires_with_pyproject(script, share
 
 
 @pytest.mark.network
-def test_upgrade_argparse_shadowed(script):
+def test_upgrade_argparse_shadowed(script: PipTestEnvironment) -> None:
     # If argparse is installed - even if shadowed for imported - we support
     # upgrading it and properly remove the older versions files.
     script.pip("install", "argparse==1.3")
@@ -727,7 +798,7 @@ def test_upgrade_argparse_shadowed(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_curdir(script, data):
+def test_install_curdir(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test installing current directory ('.').
     """
@@ -744,7 +815,7 @@ def test_install_curdir(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_pardir(script, data):
+def test_install_pardir(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test installing parent directory ('..').
     """
@@ -757,7 +828,7 @@ def test_install_pardir(script, data):
 
 
 @pytest.mark.network
-def test_install_global_option(script):
+def test_install_global_option(script: PipTestEnvironment) -> None:
     """
     Test using global distutils options.
     (In particular those that disable the actual install action)
@@ -769,7 +840,9 @@ def test_install_global_option(script):
     assert not result.files_created
 
 
-def test_install_with_hacked_egg_info(script, data):
+def test_install_with_hacked_egg_info(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     test installing a package which defines its own egg_info class
     """
@@ -779,7 +852,9 @@ def test_install_with_hacked_egg_info(script, data):
 
 
 @pytest.mark.network
-def test_install_using_install_option_and_editable(script, tmpdir):
+def test_install_using_install_option_and_editable(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test installing a tool using -e and --install-option
     """
@@ -803,7 +878,9 @@ def test_install_using_install_option_and_editable(script, tmpdir):
 @pytest.mark.xfail
 @pytest.mark.network
 @need_mercurial
-def test_install_global_option_using_editable(script, tmpdir):
+def test_install_global_option_using_editable(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test using global distutils options, but in an editable installation
     """
@@ -820,7 +897,7 @@ def test_install_global_option_using_editable(script, tmpdir):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_package_with_same_name_in_curdir(script):
+def test_install_package_with_same_name_in_curdir(script: PipTestEnvironment) -> None:
     """
     Test installing a package with the same name of a local folder
     """
@@ -839,7 +916,7 @@ def test_install_package_with_same_name_in_curdir(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_folder_using_dot_slash(script):
+def test_install_folder_using_dot_slash(script: PipTestEnvironment) -> None:
     """
     Test installing a folder using pip install ./foldername
     """
@@ -852,7 +929,7 @@ def test_install_folder_using_dot_slash(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_folder_using_slash_in_the_end(script):
+def test_install_folder_using_slash_in_the_end(script: PipTestEnvironment) -> None:
     r"""
     Test installing a folder using pip install foldername/ or foldername\
     """
@@ -865,7 +942,7 @@ def test_install_folder_using_slash_in_the_end(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_folder_using_relative_path(script):
+def test_install_folder_using_relative_path(script: PipTestEnvironment) -> None:
     """
     Test installing a folder using pip install folder1/folder2
     """
@@ -880,7 +957,7 @@ def test_install_folder_using_relative_path(script):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_package_which_contains_dev_in_name(script):
+def test_install_package_which_contains_dev_in_name(script: PipTestEnvironment) -> None:
     """
     Test installing package from PyPI which contains 'dev' in name
     """
@@ -892,7 +969,7 @@ def test_install_package_which_contains_dev_in_name(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_package_with_target(script):
+def test_install_package_with_target(script: PipTestEnvironment) -> None:
     """
     Test installing a package using pip install --target
     """
@@ -927,7 +1004,9 @@ def test_install_package_with_target(script):
 
 
 @pytest.mark.parametrize("target_option", ["--target", "-t"])
-def test_install_package_to_usersite_with_target_must_fail(script, target_option):
+def test_install_package_to_usersite_with_target_must_fail(
+    script: PipTestEnvironment, target_option: str
+) -> None:
     """
     Test that installing package to usersite with target
     must raise error
@@ -939,7 +1018,9 @@ def test_install_package_to_usersite_with_target_must_fail(script, target_option
     assert "Can not combine '--user' and '--target'" in result.stderr, str(result)
 
 
-def test_install_nonlocal_compatible_wheel(script, data):
+def test_install_nonlocal_compatible_wheel(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     target_dir = script.scratch_path / "target"
 
     # Test install with --target
@@ -984,10 +1065,10 @@ def test_install_nonlocal_compatible_wheel(script, data):
 
 
 def test_install_nonlocal_compatible_wheel_path(
-    script,
-    data,
-    resolver_variant,
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    resolver_variant: ResolverVariant,
+) -> None:
     target_dir = script.scratch_path / "target"
 
     # Test a full path requirement
@@ -1021,7 +1102,9 @@ def test_install_nonlocal_compatible_wheel_path(
 
 @pytest.mark.parametrize("opt", ("--target", "--prefix"))
 @pytest.mark.usefixtures("with_wheel")
-def test_install_with_target_or_prefix_and_scripts_no_warning(opt, script):
+def test_install_with_target_or_prefix_and_scripts_no_warning(
+    opt: str, script: PipTestEnvironment
+) -> None:
     """
     Test that installing with --target does not trigger the "script not
     in PATH" warning (issue #5201)
@@ -1058,7 +1141,7 @@ def main(): pass
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_package_with_root(script, data):
+def test_install_package_with_root(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test installing a package using pip install --root
     """
@@ -1086,7 +1169,9 @@ def test_install_package_with_root(script, data):
     assert "Looking in links: " in result.stdout
 
 
-def test_install_package_with_prefix(script, data):
+def test_install_package_with_prefix(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing a package using pip install --prefix
     """
@@ -1104,16 +1189,17 @@ def test_install_package_with_prefix(script, data):
     )
 
     rel_prefix_path = script.scratch / "prefix"
-    install_path = (
-        distutils.sysconfig.get_python_lib(prefix=rel_prefix_path)
-        /
+    install_path = join(
+        distutils.sysconfig.get_python_lib(prefix=rel_prefix_path),
         # we still test for egg-info because no-binary implies setup.py install
-        f"simple-1.0-py{pyversion}.egg-info"
+        f"simple-1.0-py{pyversion}.egg-info",
     )
     result.did_create(install_path)
 
 
-def _test_install_editable_with_prefix(script, files):
+def _test_install_editable_with_prefix(
+    script: PipTestEnvironment, files: Dict[str, str]
+) -> None:
     # make a dummy project
     pkga_path = script.scratch_path / "pkga"
     pkga_path.mkdir()
@@ -1143,7 +1229,7 @@ def _test_install_editable_with_prefix(script, files):
 
 
 @pytest.mark.network
-def test_install_editable_with_target(script):
+def test_install_editable_with_target(script: PipTestEnvironment) -> None:
     pkg_path = script.scratch_path / "pkg"
     pkg_path.mkdir()
     pkg_path.joinpath("setup.py").write_text(
@@ -1166,7 +1252,7 @@ def test_install_editable_with_target(script):
     result.did_create(script.scratch / "target" / "watching_testrunner.py")
 
 
-def test_install_editable_with_prefix_setup_py(script):
+def test_install_editable_with_prefix_setup_py(script: PipTestEnvironment) -> None:
     setup_py = """
 from setuptools import setup
 setup(name='pkga', version='0.1')
@@ -1174,7 +1260,7 @@ def test_install_editable_with_prefix_setup_py(script):
     _test_install_editable_with_prefix(script, {"setup.py": setup_py})
 
 
-def test_install_editable_with_prefix_setup_cfg(script):
+def test_install_editable_with_prefix_setup_cfg(script: PipTestEnvironment) -> None:
     setup_cfg = """[metadata]
 name = pkga
 version = 0.1
@@ -1188,7 +1274,9 @@ def test_install_editable_with_prefix_setup_cfg(script):
     )
 
 
-def test_install_package_conflict_prefix_and_user(script, data):
+def test_install_package_conflict_prefix_and_user(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing a package using pip install --prefix --user errors out
     """
@@ -1208,7 +1296,9 @@ def test_install_package_conflict_prefix_and_user(script, data):
     assert "Can not combine '--user' and '--prefix'" in result.stderr
 
 
-def test_install_package_that_emits_unicode(script, data):
+def test_install_package_that_emits_unicode(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Install a package with a setup.py that emits UTF-8 output and then fails.
 
@@ -1229,20 +1319,26 @@ def test_install_package_that_emits_unicode(script, data):
     assert "UnicodeDecodeError" not in result.stdout
 
 
-def test_install_package_with_utf8_setup(script, data):
+def test_install_package_with_utf8_setup(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Install a package with a setup.py that declares a utf-8 encoding."""
     to_install = data.packages.joinpath("SetupPyUTF8")
     script.pip("install", to_install)
 
 
-def test_install_package_with_latin1_setup(script, data):
+def test_install_package_with_latin1_setup(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Install a package with a setup.py that declares a latin-1 encoding."""
     to_install = data.packages.joinpath("SetupPyLatin1")
     script.pip("install", to_install)
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_url_req_case_mismatch_no_index(script, data):
+def test_url_req_case_mismatch_no_index(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     tar ball url requirements (with no egg fragment), that happen to have upper
     case project names, should be considered equal to later requirements that
@@ -1264,7 +1360,9 @@ def test_url_req_case_mismatch_no_index(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_url_req_case_mismatch_file_index(script, data):
+def test_url_req_case_mismatch_file_index(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     tar ball url requirements (with no egg fragment), that happen to have upper
     case project names, should be considered equal to later requirements that
@@ -1292,7 +1390,9 @@ def test_url_req_case_mismatch_file_index(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_url_incorrect_case_no_index(script, data):
+def test_url_incorrect_case_no_index(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Same as test_url_req_case_mismatch_no_index, except testing for the case
     where the incorrect case is given in the name of the package to install
@@ -1314,7 +1414,9 @@ def test_url_incorrect_case_no_index(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_url_incorrect_case_file_index(script, data):
+def test_url_incorrect_case_file_index(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Same as test_url_req_case_mismatch_file_index, except testing for the case
     where the incorrect case is given in the name of the package to install
@@ -1340,7 +1442,7 @@ def test_url_incorrect_case_file_index(script, data):
 
 
 @pytest.mark.network
-def test_compiles_pyc(script):
+def test_compiles_pyc(script: PipTestEnvironment) -> None:
     """
     Test installing with --compile on
     """
@@ -1351,17 +1453,14 @@ def test_compiles_pyc(script):
     #   any of them
     exists = [
         os.path.exists(script.site_packages_path / "initools/__init__.pyc"),
+        *glob.glob(script.site_packages_path / "initools/__pycache__/__init__*.pyc"),
     ]
 
-    exists += glob.glob(
-        script.site_packages_path / "initools/__pycache__/__init__*.pyc"
-    )
-
     assert any(exists)
 
 
 @pytest.mark.network
-def test_no_compiles_pyc(script):
+def test_no_compiles_pyc(script: PipTestEnvironment) -> None:
     """
     Test installing from wheel with --compile on
     """
@@ -1372,16 +1471,15 @@ def test_no_compiles_pyc(script):
     #   any of them
     exists = [
         os.path.exists(script.site_packages_path / "initools/__init__.pyc"),
+        *glob.glob(script.site_packages_path / "initools/__pycache__/__init__*.pyc"),
     ]
 
-    exists += glob.glob(
-        script.site_packages_path / "initools/__pycache__/__init__*.pyc"
-    )
-
     assert not any(exists)
 
 
-def test_install_upgrade_editable_depending_on_other_editable(script):
+def test_install_upgrade_editable_depending_on_other_editable(
+    script: PipTestEnvironment,
+) -> None:
     script.scratch_path.joinpath("pkga").mkdir()
     pkga_path = script.scratch_path / "pkga"
     pkga_path.joinpath("setup.py").write_text(
@@ -1414,7 +1512,9 @@ def test_install_upgrade_editable_depending_on_other_editable(script):
     assert "pkgb==0.1" in result.stdout
 
 
-def test_install_subprocess_output_handling(script, data):
+def test_install_subprocess_output_handling(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     args = ["install", data.src.joinpath("chattymodule")]
 
     # Regular install should not show output from the chatty setup.py
@@ -1440,7 +1540,7 @@ def test_install_subprocess_output_handling(script, data):
     assert 1 == result.stderr.count("I DIE, I DIE")
 
 
-def test_install_log(script, data, tmpdir):
+def test_install_log(script: PipTestEnvironment, data: TestData, tmpdir: Path) -> None:
     # test that verbose logs go to "--log" file
     f = tmpdir.joinpath("log.txt")
     args = [f"--log={f}", "install", data.src.joinpath("chattymodule")]
@@ -1451,7 +1551,7 @@ def test_install_log(script, data, tmpdir):
         assert 2 == fp.read().count("HELLO FROM CHATTYMODULE")
 
 
-def test_install_topological_sort(script, data):
+def test_install_topological_sort(script: PipTestEnvironment, data: TestData) -> None:
     args = ["install", "TopoRequires4", "--no-index", "-f", data.packages]
     res = str(script.pip(*args))
     order1 = "TopoRequires, TopoRequires2, TopoRequires3, TopoRequires4"
@@ -1460,13 +1560,13 @@ def test_install_topological_sort(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_wheel_broken(script):
+def test_install_wheel_broken(script: PipTestEnvironment) -> None:
     res = script.pip_install_local("wheelbroken", expect_stderr=True)
     assert "Successfully installed wheelbroken-0.1" in str(res), str(res)
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_cleanup_after_failed_wheel(script):
+def test_cleanup_after_failed_wheel(script: PipTestEnvironment) -> None:
     res = script.pip_install_local("wheelbrokenafter", expect_stderr=True)
     # One of the effects of not cleaning up is broken scripts:
     script_py = script.bin_path / "script.py"
@@ -1480,7 +1580,7 @@ def test_cleanup_after_failed_wheel(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_builds_wheels(script, data):
+def test_install_builds_wheels(script: PipTestEnvironment, data: TestData) -> None:
     # We need to use a subprocess to get the right value on Windows.
     res = script.run(
         "python",
@@ -1528,7 +1628,9 @@ def test_install_builds_wheels(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_no_binary_disables_building_wheels(script, data):
+def test_install_no_binary_disables_building_wheels(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.packages.joinpath("requires_wheelbroken_upper")
     res = script.pip(
         "install",
@@ -1560,7 +1662,9 @@ def test_install_no_binary_disables_building_wheels(script, data):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_no_binary_builds_pep_517_wheel(script, data):
+def test_install_no_binary_builds_pep_517_wheel(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.packages.joinpath("pep517_setup_and_pyproject")
     res = script.pip("install", "--no-binary=:all:", "-f", data.find_links, to_install)
     expected = "Successfully installed pep517-setup-and-pyproject"
@@ -1573,7 +1677,9 @@ def test_install_no_binary_builds_pep_517_wheel(script, data):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_no_binary_uses_local_backend(script, data, tmpdir):
+def test_install_no_binary_uses_local_backend(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     to_install = data.packages.joinpath("pep517_wrapper_buildsys")
     script.environ["PIP_TEST_MARKER_FILE"] = marker = str(tmpdir / "marker")
     res = script.pip("install", "--no-binary=:all:", "-f", data.find_links, to_install)
@@ -1585,7 +1691,9 @@ def test_install_no_binary_uses_local_backend(script, data, tmpdir):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_no_binary_disables_cached_wheels(script, data):
+def test_install_no_binary_disables_cached_wheels(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     # Seed the cache
     script.pip("install", "--no-index", "-f", data.find_links, "upper")
     script.pip("uninstall", "upper", "-y")
@@ -1605,7 +1713,9 @@ def test_install_no_binary_disables_cached_wheels(script, data):
     assert "Running setup.py install for upper" in str(res), str(res)
 
 
-def test_install_editable_with_wrong_egg_name(script, resolver_variant):
+def test_install_editable_with_wrong_egg_name(
+    script: PipTestEnvironment, resolver_variant: ResolverVariant
+) -> None:
     script.scratch_path.joinpath("pkga").mkdir()
     pkga_path = script.scratch_path / "pkga"
     pkga_path.joinpath("setup.py").write_text(
@@ -1634,7 +1744,7 @@ def test_install_editable_with_wrong_egg_name(script, resolver_variant):
         assert "Successfully installed pkga" in str(result), str(result)
 
 
-def test_install_tar_xz(script, data):
+def test_install_tar_xz(script: PipTestEnvironment, data: TestData) -> None:
     try:
         import lzma  # noqa
     except ImportError:
@@ -1643,7 +1753,7 @@ def test_install_tar_xz(script, data):
     assert "Successfully installed singlemodule-0.0.1" in res.stdout, res
 
 
-def test_install_tar_lzma(script, data):
+def test_install_tar_lzma(script: PipTestEnvironment, data: TestData) -> None:
     try:
         import lzma  # noqa
     except ImportError:
@@ -1652,7 +1762,7 @@ def test_install_tar_lzma(script, data):
     assert "Successfully installed singlemodule-0.0.1" in res.stdout, res
 
 
-def test_double_install(script):
+def test_double_install(script: PipTestEnvironment) -> None:
     """
     Test double install passing with two same version requirements
     """
@@ -1661,7 +1771,9 @@ def test_double_install(script):
     assert msg not in result.stderr
 
 
-def test_double_install_fail(script, resolver_variant):
+def test_double_install_fail(
+    script: PipTestEnvironment, resolver_variant: ResolverVariant
+) -> None:
     """
     Test double install failing with two different version requirements
     """
@@ -1677,13 +1789,13 @@ def test_double_install_fail(script, resolver_variant):
         assert msg in result.stderr
 
 
-def _get_expected_error_text():
+def _get_expected_error_text() -> str:
     return ("Package 'pkga' requires a different Python: {} not in '<1.0'").format(
         ".".join(map(str, sys.version_info[:3]))
     )
 
 
-def test_install_incompatible_python_requires(script):
+def test_install_incompatible_python_requires(script: PipTestEnvironment) -> None:
     script.scratch_path.joinpath("pkga").mkdir()
     pkga_path = script.scratch_path / "pkga"
     pkga_path.joinpath("setup.py").write_text(
@@ -1700,7 +1812,9 @@ def test_install_incompatible_python_requires(script):
     assert _get_expected_error_text() in result.stderr, str(result)
 
 
-def test_install_incompatible_python_requires_editable(script):
+def test_install_incompatible_python_requires_editable(
+    script: PipTestEnvironment,
+) -> None:
     script.scratch_path.joinpath("pkga").mkdir()
     pkga_path = script.scratch_path / "pkga"
     pkga_path.joinpath("setup.py").write_text(
@@ -1718,7 +1832,7 @@ def test_install_incompatible_python_requires_editable(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_incompatible_python_requires_wheel(script):
+def test_install_incompatible_python_requires_wheel(script: PipTestEnvironment) -> None:
     script.scratch_path.joinpath("pkga").mkdir()
     pkga_path = script.scratch_path / "pkga"
     pkga_path.joinpath("setup.py").write_text(
@@ -1744,7 +1858,7 @@ def test_install_incompatible_python_requires_wheel(script):
     assert _get_expected_error_text() in result.stderr, str(result)
 
 
-def test_install_compatible_python_requires(script):
+def test_install_compatible_python_requires(script: PipTestEnvironment) -> None:
     script.scratch_path.joinpath("pkga").mkdir()
     pkga_path = script.scratch_path / "pkga"
     pkga_path.joinpath("setup.py").write_text(
@@ -1762,7 +1876,7 @@ def test_install_compatible_python_requires(script):
 
 
 @pytest.mark.network
-def test_install_pep508_with_url(script):
+def test_install_pep508_with_url(script: PipTestEnvironment) -> None:
     res = script.pip(
         "install",
         "--no-index",
@@ -1775,7 +1889,9 @@ def test_install_pep508_with_url(script):
 
 
 @pytest.mark.network
-def test_install_pep508_with_url_in_install_requires(script):
+def test_install_pep508_with_url_in_install_requires(
+    script: PipTestEnvironment,
+) -> None:
     pkga_path = create_test_package_with_setup(
         script,
         name="pkga",
@@ -1793,7 +1909,9 @@ def test_install_pep508_with_url_in_install_requires(script):
 
 @pytest.mark.network
 @pytest.mark.parametrize("index", (PyPI.simple_url, TestPyPI.simple_url))
-def test_install_from_test_pypi_with_ext_url_dep_is_blocked(script, index):
+def test_install_from_test_pypi_with_ext_url_dep_is_blocked(
+    script: PipTestEnvironment, index: str
+) -> None:
     res = script.pip(
         "install",
         "--index-url",
@@ -1817,13 +1935,17 @@ def test_install_from_test_pypi_with_ext_url_dep_is_blocked(script, index):
 @pytest.mark.xfail(
     reason="No longer possible to trigger the warning with either --prefix or --target"
 )
-def test_installing_scripts_outside_path_prints_warning(script):
+def test_installing_scripts_outside_path_prints_warning(
+    script: PipTestEnvironment,
+) -> None:
     result = script.pip_install_local("--prefix", script.scratch_path, "script_wheel1")
     assert "Successfully installed script-wheel1" in result.stdout, str(result)
     assert "--no-warn-script-location" in result.stderr
 
 
-def test_installing_scripts_outside_path_can_suppress_warning(script):
+def test_installing_scripts_outside_path_can_suppress_warning(
+    script: PipTestEnvironment,
+) -> None:
     result = script.pip_install_local(
         "--prefix", script.scratch_path, "--no-warn-script-location", "script_wheel1"
     )
@@ -1831,13 +1953,17 @@ def test_installing_scripts_outside_path_can_suppress_warning(script):
     assert "--no-warn-script-location" not in result.stderr
 
 
-def test_installing_scripts_on_path_does_not_print_warning(script):
+def test_installing_scripts_on_path_does_not_print_warning(
+    script: PipTestEnvironment,
+) -> None:
     result = script.pip_install_local("script_wheel1")
     assert "Successfully installed script-wheel1" in result.stdout, str(result)
     assert "--no-warn-script-location" not in result.stderr
 
 
-def test_installed_files_recorded_in_deterministic_order(script, data):
+def test_installed_files_recorded_in_deterministic_order(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Ensure that we record the files installed by a package in a deterministic
     order, to make installs reproducible.
@@ -1857,7 +1983,9 @@ def test_installed_files_recorded_in_deterministic_order(script, data):
     assert installed_files_lines == sorted(installed_files_lines)
 
 
-def test_install_conflict_results_in_warning(script, data):
+def test_install_conflict_results_in_warning(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     pkgA_path = create_test_package_with_setup(
         script,
         name="pkgA",
@@ -1885,7 +2013,9 @@ def test_install_conflict_results_in_warning(script, data):
     assert "Successfully installed pkgB-2.0" in result2.stdout, str(result2)
 
 
-def test_install_conflict_warning_can_be_suppressed(script, data):
+def test_install_conflict_warning_can_be_suppressed(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     pkgA_path = create_test_package_with_setup(
         script,
         name="pkgA",
@@ -1907,7 +2037,9 @@ def test_install_conflict_warning_can_be_suppressed(script, data):
     assert "Successfully installed pkgB-2.0" in result2.stdout, str(result2)
 
 
-def test_target_install_ignores_distutils_config_install_prefix(script):
+def test_target_install_ignores_distutils_config_install_prefix(
+    script: PipTestEnvironment,
+) -> None:
     prefix = script.scratch_path / "prefix"
     distutils_config = Path(
         os.path.expanduser("~"),
@@ -1933,7 +2065,7 @@ def test_target_install_ignores_distutils_config_install_prefix(script):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_user_config_accepted(script):
+def test_user_config_accepted(script: PipTestEnvironment) -> None:
     # user set in the config file is parsed as 0/1 instead of True/False.
     # Check that this doesn't cause a problem.
     config_file = script.scratch_path / "pip.conf"
@@ -1956,8 +2088,12 @@ def test_user_config_accepted(script):
 )
 @pytest.mark.parametrize("use_module", [True, False])
 def test_install_pip_does_not_modify_pip_when_satisfied(
-    script, install_args, expected_message, use_module, resolver_variant
-):
+    script: PipTestEnvironment,
+    install_args: List[str],
+    expected_message: str,
+    use_module: bool,
+    resolver_variant: ResolverVariant,
+) -> None:
     """
     Test it doesn't upgrade the pip if it already satisfies the requirement.
     """
@@ -1967,7 +2103,7 @@ def test_install_pip_does_not_modify_pip_when_satisfied(
     assert expected_message in result.stdout, str(result)
 
 
-def test_ignore_yanked_file(script, data):
+def test_ignore_yanked_file(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test ignore a "yanked" file.
     """
@@ -1981,7 +2117,9 @@ def test_ignore_yanked_file(script, data):
     assert "Successfully installed simple-2.0\n" in result.stdout, str(result)
 
 
-def test_invalid_index_url_argument(script, shared_data):
+def test_invalid_index_url_argument(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
     """
     Test the behaviour of an invalid --index-url argument
     """
@@ -2000,7 +2138,9 @@ def test_invalid_index_url_argument(script, shared_data):
     ) in result.stderr, str(result)
 
 
-def test_valid_index_url_argument(script, shared_data):
+def test_valid_index_url_argument(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
     """
     Test the behaviour of an valid --index-url argument
     """
@@ -2010,7 +2150,9 @@ def test_valid_index_url_argument(script, shared_data):
     assert "Successfully installed Dinner" in result.stdout, str(result)
 
 
-def test_install_yanked_file_and_print_warning(script, data):
+def test_install_yanked_file_and_print_warning(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test install a "yanked" file and print a warning.
 
@@ -2037,7 +2179,12 @@ def test_install_yanked_file_and_print_warning(script, data):
         ("--trusted-host", "localhost"),
     ],
 )
-def test_install_sends_client_cert(install_args, script, cert_factory, data):
+def test_install_sends_client_cert(
+    install_args: Tuple[str, ...],
+    script: PipTestEnvironment,
+    cert_factory: CertFactory,
+    data: TestData,
+) -> None:
     cert_path = cert_factory()
     ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
     ctx.load_cert_chain(cert_path, cert_path)
@@ -2073,7 +2220,7 @@ def test_install_sends_client_cert(install_args, script, cert_factory, data):
         assert environ["SSL_CLIENT_CERT"]
 
 
-def test_install_skip_work_dir_pkg(script, data):
+def test_install_skip_work_dir_pkg(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test that install of a package in working directory
     should pass on the second attempt after an install
@@ -2104,7 +2251,9 @@ def test_install_skip_work_dir_pkg(script, data):
 @pytest.mark.parametrize(
     "package_name", ("simple-package", "simple_package", "simple.package")
 )
-def test_install_verify_package_name_normalization(script, package_name):
+def test_install_verify_package_name_normalization(
+    script: PipTestEnvironment, package_name: str
+) -> None:
 
     """
     Test that install of a package again using a name which
@@ -2121,7 +2270,9 @@ def test_install_verify_package_name_normalization(script, package_name):
     assert "Requirement already satisfied: {}".format(package_name) in result.stdout
 
 
-def test_install_logs_pip_version_in_debug(script, shared_data):
+def test_install_logs_pip_version_in_debug(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
     fake_package = shared_data.packages / "simple-2.0.tar.gz"
     result = script.pip("install", "-v", fake_package)
     pattern = "Using pip .* from .*"
diff --git a/tests/functional/test_install_check.py b/tests/functional/test_install_check.py
index c3f1e82f27d..8a8a7c93a80 100644
--- a/tests/functional/test_install_check.py
+++ b/tests/functional/test_install_check.py
@@ -1,12 +1,14 @@
-from tests.lib import create_test_package_with_setup
+from typing import Iterable
 
+from tests.lib import PipTestEnvironment, create_test_package_with_setup
 
-def assert_contains_expected_lines(string, expected_lines):
+
+def assert_contains_expected_lines(string: str, expected_lines: Iterable[str]) -> None:
     for expected_line in expected_lines:
         assert (expected_line + "\n") in string
 
 
-def test_check_install_canonicalization(script):
+def test_check_install_canonicalization(script: PipTestEnvironment) -> None:
     pkga_path = create_test_package_with_setup(
         script,
         name="pkgA",
@@ -65,7 +67,9 @@ def test_check_install_canonicalization(script):
     assert result.returncode == 0
 
 
-def test_check_install_does_not_warn_for_out_of_graph_issues(script):
+def test_check_install_does_not_warn_for_out_of_graph_issues(
+    script: PipTestEnvironment,
+) -> None:
     pkg_broken_path = create_test_package_with_setup(
         script,
         name="broken",
diff --git a/tests/functional/test_install_cleanup.py b/tests/functional/test_install_cleanup.py
index 02b2a1967b0..c0ea5a425b9 100644
--- a/tests/functional/test_install_cleanup.py
+++ b/tests/functional/test_install_cleanup.py
@@ -2,10 +2,14 @@
 
 import pytest
 
+from tests.lib import PipTestEnvironment, TestData
+
 
 @pytest.mark.network
 @pytest.mark.xfail(reason="The --build option was removed")
-def test_no_clean_option_blocks_cleaning_after_install(script, data):
+def test_no_clean_option_blocks_cleaning_after_install(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test --no-clean option blocks cleaning after install
     """
@@ -28,7 +32,7 @@ def test_no_clean_option_blocks_cleaning_after_install(script, data):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_pep517_no_legacy_cleanup(script, data):
+def test_pep517_no_legacy_cleanup(script: PipTestEnvironment, data: TestData) -> None:
     """Test a PEP 517 failed build does not attempt a legacy cleanup"""
     to_install = data.packages.joinpath("pep517_wrapper_buildsys")
     script.environ["PIP_TEST_FAIL_BUILD_WHEEL"] = "1"
diff --git a/tests/functional/test_install_compat.py b/tests/functional/test_install_compat.py
index ab13147e39a..4b6b46b02df 100644
--- a/tests/functional/test_install_compat.py
+++ b/tests/functional/test_install_compat.py
@@ -7,11 +7,11 @@
 import pytest
 
 from tests.lib import pyversion  # noqa: F401
-from tests.lib import assert_all_changes
+from tests.lib import PipTestEnvironment, TestData, assert_all_changes
 
 
 @pytest.mark.network
-def test_debian_egg_name_workaround(script):
+def test_debian_egg_name_workaround(script: PipTestEnvironment) -> None:
     """
     We can uninstall packages installed with the pyversion removed from the
     egg-info metadata directory name.
@@ -50,7 +50,9 @@ def test_debian_egg_name_workaround(script):
     assert_all_changes(result, result2, [script.venv / "build", "cache"])
 
 
-def test_setup_py_with_dos_line_endings(script, data):
+def test_setup_py_with_dos_line_endings(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     It doesn't choke on a setup.py file that uses DOS line endings (\\r\\n).
 
diff --git a/tests/functional/test_install_config.py b/tests/functional/test_install_config.py
index a80256d2b90..5eae0401aa7 100644
--- a/tests/functional/test_install_config.py
+++ b/tests/functional/test_install_config.py
@@ -5,6 +5,8 @@
 
 import pytest
 
+from tests.conftest import CertFactory, MockServer
+from tests.lib import PipTestEnvironment, TestData
 from tests.lib.server import (
     authorization_response,
     file_response,
@@ -12,9 +14,10 @@
     package_page,
     server_running,
 )
+from tests.lib.venv import VirtualEnvironment
 
 
-def test_options_from_env_vars(script):
+def test_options_from_env_vars(script: PipTestEnvironment) -> None:
     """
     Test if ConfigOptionParser reads env vars (e.g. not using PyPI here)
 
@@ -27,7 +30,9 @@ def test_options_from_env_vars(script):
     assert msg.lower() in result.stdout.lower(), str(result)
 
 
-def test_command_line_options_override_env_vars(script, virtualenv):
+def test_command_line_options_override_env_vars(
+    script: PipTestEnvironment, virtualenv: VirtualEnvironment
+) -> None:
     """
     Test that command line options override environmental variables.
 
@@ -49,7 +54,9 @@ def test_command_line_options_override_env_vars(script, virtualenv):
 
 
 @pytest.mark.network
-def test_env_vars_override_config_file(script, virtualenv):
+def test_env_vars_override_config_file(
+    script: PipTestEnvironment, virtualenv: VirtualEnvironment
+) -> None:
     """
     Test that environmental variables override settings in config files.
     """
@@ -79,7 +86,9 @@ def test_env_vars_override_config_file(script, virtualenv):
 
 
 @pytest.mark.network
-def test_command_line_append_flags(script, virtualenv, data):
+def test_command_line_append_flags(
+    script: PipTestEnvironment, virtualenv: VirtualEnvironment, data: TestData
+) -> None:
     """
     Test command line flags that append to defaults set by environmental
     variables.
@@ -117,7 +126,9 @@ def test_command_line_append_flags(script, virtualenv, data):
 
 
 @pytest.mark.network
-def test_command_line_appends_correctly(script, data):
+def test_command_line_appends_correctly(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test multiple appending options set by environmental variables.
 
@@ -140,7 +151,12 @@ def test_command_line_appends_correctly(script, data):
     ), f"stdout: {result.stdout}"
 
 
-def test_config_file_override_stack(script, virtualenv, mock_server, shared_data):
+def test_config_file_override_stack(
+    script: PipTestEnvironment,
+    virtualenv: VirtualEnvironment,
+    mock_server: MockServer,
+    shared_data: TestData,
+) -> None:
     """
     Test config files (global, overriding a global config with a
     local, overriding all with a command line flag).
@@ -204,7 +220,9 @@ def test_config_file_override_stack(script, virtualenv, mock_server, shared_data
     assert requests[3]["PATH_INFO"] == "/files/INITools-0.2.tar.gz"
 
 
-def test_options_from_venv_config(script, virtualenv):
+def test_options_from_venv_config(
+    script: PipTestEnvironment, virtualenv: VirtualEnvironment
+) -> None:
     """
     Test if ConfigOptionParser reads a virtualenv-local config file
 
@@ -223,7 +241,9 @@ def test_options_from_venv_config(script, virtualenv):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_no_binary_via_config_disables_cached_wheels(script, data):
+def test_install_no_binary_via_config_disables_cached_wheels(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     config_file = tempfile.NamedTemporaryFile(mode="wt", delete=False)
     try:
         script.environ["PIP_CONFIG_FILE"] = config_file.name
@@ -248,7 +268,9 @@ def test_install_no_binary_via_config_disables_cached_wheels(script, data):
     assert "Running setup.py install for upper" in str(res), str(res)
 
 
-def test_prompt_for_authentication(script, data, cert_factory):
+def test_prompt_for_authentication(
+    script: PipTestEnvironment, data: TestData, cert_factory: CertFactory
+) -> None:
     """Test behaviour while installing from a index url
     requiring authentication
     """
@@ -286,7 +308,9 @@ def test_prompt_for_authentication(script, data, cert_factory):
     assert f"User for {server.host}:{server.port}" in result.stdout, str(result)
 
 
-def test_do_not_prompt_for_authentication(script, data, cert_factory):
+def test_do_not_prompt_for_authentication(
+    script: PipTestEnvironment, data: TestData, cert_factory: CertFactory
+) -> None:
     """Test behaviour if --no-input option is given while installing
     from a index url requiring authentication
     """
@@ -327,7 +351,12 @@ def test_do_not_prompt_for_authentication(script, data, cert_factory):
 
 
 @pytest.mark.parametrize("auth_needed", (True, False))
-def test_prompt_for_keyring_if_needed(script, data, cert_factory, auth_needed):
+def test_prompt_for_keyring_if_needed(
+    script: PipTestEnvironment,
+    data: TestData,
+    cert_factory: CertFactory,
+    auth_needed: bool,
+) -> None:
     """Test behaviour while installing from a index url
     requiring authentication and keyring is possible.
     """
diff --git a/tests/functional/test_install_direct_url.py b/tests/functional/test_install_direct_url.py
index 5dd7482cf78..9d5e0612ea9 100644
--- a/tests/functional/test_install_direct_url.py
+++ b/tests/functional/test_install_direct_url.py
@@ -1,17 +1,18 @@
 import pytest
 
-from tests.lib import _create_test_package, path_to_url
+from pip._internal.models.direct_url import VcsInfo
+from tests.lib import PipTestEnvironment, TestData, _create_test_package, path_to_url
 from tests.lib.direct_url import get_created_direct_url
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_find_links_no_direct_url(script):
+def test_install_find_links_no_direct_url(script: PipTestEnvironment) -> None:
     result = script.pip_install_local("simple")
     assert not get_created_direct_url(result, "simple")
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_vcs_editable_no_direct_url(script):
+def test_install_vcs_editable_no_direct_url(script: PipTestEnvironment) -> None:
     pkg_path = _create_test_package(script, name="testpkg")
     args = ["install", "-e", "git+%s#egg=testpkg" % path_to_url(pkg_path)]
     result = script.pip(*args)
@@ -21,7 +22,7 @@ def test_install_vcs_editable_no_direct_url(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_vcs_non_editable_direct_url(script):
+def test_install_vcs_non_editable_direct_url(script: PipTestEnvironment) -> None:
     pkg_path = _create_test_package(script, name="testpkg")
     url = path_to_url(pkg_path)
     args = ["install", f"git+{url}#egg=testpkg"]
@@ -29,11 +30,12 @@ def test_install_vcs_non_editable_direct_url(script):
     direct_url = get_created_direct_url(result, "testpkg")
     assert direct_url
     assert direct_url.url == url
+    assert isinstance(direct_url.info, VcsInfo)
     assert direct_url.info.vcs == "git"
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_archive_direct_url(script, data):
+def test_install_archive_direct_url(script: PipTestEnvironment, data: TestData) -> None:
     req = "simple @ " + path_to_url(data.packages / "simple-2.0.tar.gz")
     assert req.startswith("simple @ file://")
     result = script.pip("install", req)
@@ -42,7 +44,7 @@ def test_install_archive_direct_url(script, data):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_vcs_constraint_direct_url(script):
+def test_install_vcs_constraint_direct_url(script: PipTestEnvironment) -> None:
     constraints_file = script.scratch_path / "constraints.txt"
     constraints_file.write_text(
         "git+https://github.com/pypa/pip-test-package"
@@ -54,7 +56,7 @@ def test_install_vcs_constraint_direct_url(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_vcs_constraint_direct_file_url(script):
+def test_install_vcs_constraint_direct_file_url(script: PipTestEnvironment) -> None:
     pkg_path = _create_test_package(script, name="testpkg")
     url = path_to_url(pkg_path)
     constraints_file = script.scratch_path / "constraints.txt"
diff --git a/tests/functional/test_install_extras.py b/tests/functional/test_install_extras.py
index b950e5bae02..c6cef00fa9c 100644
--- a/tests/functional/test_install_extras.py
+++ b/tests/functional/test_install_extras.py
@@ -4,9 +4,11 @@
 
 import pytest
 
+from tests.lib import PipTestEnvironment, ResolverVariant, TestData
+
 
 @pytest.mark.network
-def test_simple_extras_install_from_pypi(script):
+def test_simple_extras_install_from_pypi(script: PipTestEnvironment) -> None:
     """
     Test installing a package from PyPI using extras dependency Paste[openid].
     """
@@ -19,7 +21,7 @@ def test_simple_extras_install_from_pypi(script):
     result.did_create(initools_folder)
 
 
-def test_extras_after_wheel(script, data):
+def test_extras_after_wheel(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test installing a package with extras after installing from a wheel.
     """
@@ -47,7 +49,7 @@ def test_extras_after_wheel(script, data):
 
 
 @pytest.mark.network
-def test_no_extras_uninstall(script):
+def test_no_extras_uninstall(script: PipTestEnvironment) -> None:
     """
     No extras dependency gets uninstalled when the root package is uninstalled
     """
@@ -64,7 +66,9 @@ def test_no_extras_uninstall(script):
     assert initools_folder not in result2.files_deleted, result.files_deleted
 
 
-def test_nonexistent_extra_warns_user_no_wheel(script, data):
+def test_nonexistent_extra_warns_user_no_wheel(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     A warning is logged telling the user that the extra option they requested
     does not exist in the project they are wishing to install.
@@ -84,7 +88,9 @@ def test_nonexistent_extra_warns_user_no_wheel(script, data):
     )
 
 
-def test_nonexistent_extra_warns_user_with_wheel(script, data):
+def test_nonexistent_extra_warns_user_with_wheel(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     A warning is logged telling the user that the extra option they requested
     does not exist in the project they are wishing to install.
@@ -101,7 +107,9 @@ def test_nonexistent_extra_warns_user_with_wheel(script, data):
     assert "simplewheel 2.0 does not provide the extra 'nonexistent'" in result.stderr
 
 
-def test_nonexistent_options_listed_in_order(script, data):
+def test_nonexistent_options_listed_in_order(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Warn the user for each extra that doesn't exist.
     """
@@ -118,7 +126,9 @@ def test_nonexistent_options_listed_in_order(script, data):
     assert matches == ["nonexistent", "nope"]
 
 
-def test_install_fails_if_extra_at_end(script, data):
+def test_install_fails_if_extra_at_end(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Fail if order of specifiers and extras is incorrect.
 
@@ -140,7 +150,7 @@ def test_install_fails_if_extra_at_end(script, data):
     assert "Extras after version" in result.stderr
 
 
-def test_install_special_extra(script):
+def test_install_special_extra(script: PipTestEnvironment) -> None:
     # Check that uppercase letters and '-' are dealt with
     # make a dummy project
     pkga_path = script.scratch_path / "pkga"
@@ -165,7 +175,7 @@ def test_install_special_extra(script):
     ) in result.stderr, str(result)
 
 
-def test_install_requirements_no_r_flag(script):
+def test_install_requirements_no_r_flag(script: PipTestEnvironment) -> None:
     """Beginners sometimes forget the -r and this leads to confusion"""
     result = script.pip("install", "requirements.txt", expect_error=True)
     assert 'literally named "requirements.txt"' in result.stdout
@@ -182,12 +192,12 @@ def test_install_requirements_no_r_flag(script):
 )
 @pytest.mark.usefixtures("data")
 def test_install_extra_merging(
-    script,
-    resolver_variant,
-    extra_to_install,
-    simple_version,
-    fails_on_legacy,
-):
+    script: PipTestEnvironment,
+    resolver_variant: ResolverVariant,
+    extra_to_install: str,
+    simple_version: str,
+    fails_on_legacy: bool,
+) -> None:
     # Check that extra specifications in the extras section are honoured.
     pkga_path = script.scratch_path / "pkga"
     pkga_path.mkdir()
diff --git a/tests/functional/test_install_force_reinstall.py b/tests/functional/test_install_force_reinstall.py
index 839469a785e..9c49d58c4b7 100644
--- a/tests/functional/test_install_force_reinstall.py
+++ b/tests/functional/test_install_force_reinstall.py
@@ -1,9 +1,11 @@
 import os
 
-from tests.lib import assert_all_changes
+from tests.lib import PipTestEnvironment, assert_all_changes
 
 
-def check_installed_version(script, package, expected):
+def check_installed_version(
+    script: PipTestEnvironment, package: str, expected: str
+) -> None:
     result = script.pip("show", package)
     lines = result.stdout.splitlines()
     version = None
@@ -14,7 +16,9 @@ def check_installed_version(script, package, expected):
     assert version == expected, f"version {version} != {expected}"
 
 
-def check_force_reinstall(script, specifier, expected):
+def check_force_reinstall(
+    script: PipTestEnvironment, specifier: str, expected: str
+) -> None:
     """
     Args:
       specifier: the requirement specifier to force-reinstall.
@@ -39,7 +43,7 @@ def check_force_reinstall(script, specifier, expected):
     assert_all_changes(result, result3, [script.venv / "build", "cache"])
 
 
-def test_force_reinstall_with_no_version_specifier(script):
+def test_force_reinstall_with_no_version_specifier(script: PipTestEnvironment) -> None:
     """
     Check --force-reinstall when there is no version specifier and the
     installed version is not the newest version.
@@ -47,7 +51,9 @@ def test_force_reinstall_with_no_version_specifier(script):
     check_force_reinstall(script, "simplewheel", "2.0")
 
 
-def test_force_reinstall_with_same_version_specifier(script):
+def test_force_reinstall_with_same_version_specifier(
+    script: PipTestEnvironment,
+) -> None:
     """
     Check --force-reinstall when the version specifier equals the installed
     version and the installed version is not the newest version.
diff --git a/tests/functional/test_install_index.py b/tests/functional/test_install_index.py
index 962a64008db..3308de504ac 100644
--- a/tests/functional/test_install_index.py
+++ b/tests/functional/test_install_index.py
@@ -4,9 +4,11 @@
 
 import pytest
 
+from tests.lib import PipTestEnvironment, TestData
+
 
 @pytest.mark.usefixtures("with_wheel")
-def test_find_links_relative_path(script, data):
+def test_find_links_relative_path(script: PipTestEnvironment, data: TestData) -> None:
     """Test find-links as a relative path."""
     result = script.pip(
         "install",
@@ -23,7 +25,9 @@ def test_find_links_relative_path(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_find_links_requirements_file_relative_path(script, data):
+def test_find_links_requirements_file_relative_path(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Test find-links as a relative path to a reqs file."""
     script.scratch_path.joinpath("test-req.txt").write_text(
         textwrap.dedent(
@@ -49,7 +53,9 @@ def test_find_links_requirements_file_relative_path(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_from_file_index_hash_link(script, data):
+def test_install_from_file_index_hash_link(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test that a pkg can be installed from a file:// index using a link with a
     hash
@@ -60,7 +66,7 @@ def test_install_from_file_index_hash_link(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_file_index_url_quoting(script, data):
+def test_file_index_url_quoting(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test url quoting of file index url with a space
     """
diff --git a/tests/functional/test_install_reqs.py b/tests/functional/test_install_reqs.py
index 520ad01897b..45b1edff9e2 100644
--- a/tests/functional/test_install_reqs.py
+++ b/tests/functional/test_install_reqs.py
@@ -1,10 +1,14 @@
 import json
 import os
 import textwrap
+from typing import Any, Callable
 
 import pytest
 
 from tests.lib import (
+    PipTestEnvironment,
+    ResolverVariant,
+    TestData,
     _create_test_package_with_subdirectory,
     create_basic_sdist_for_package,
     create_basic_wheel_for_package,
@@ -17,16 +21,18 @@
 
 
 class ArgRecordingSdist:
-    def __init__(self, sdist_path, args_path):
+    def __init__(self, sdist_path: Path, args_path: Path) -> None:
         self.sdist_path = sdist_path
         self._args_path = args_path
 
-    def args(self):
+    def args(self) -> Any:
         return json.loads(self._args_path.read_text())
 
 
 @pytest.fixture()
-def arg_recording_sdist_maker(script):
+def arg_recording_sdist_maker(
+    script: PipTestEnvironment,
+) -> Callable[[str], ArgRecordingSdist]:
     arg_writing_setup_py = textwrap.dedent(
         """
         import io
@@ -58,7 +64,7 @@ def _arg_recording_sdist_maker(name: str) -> ArgRecordingSdist:
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_requirements_file(script):
+def test_requirements_file(script: PipTestEnvironment) -> None:
     """
     Test installing from a requirements file.
 
@@ -81,7 +87,7 @@ def test_requirements_file(script):
     assert result.files_created[script.site_packages / fn].dir
 
 
-def test_schema_check_in_requirements_file(script):
+def test_schema_check_in_requirements_file(script: PipTestEnvironment) -> None:
     """
     Test installing from a requirements file with an invalid vcs schema..
 
@@ -109,7 +115,9 @@ def test_schema_check_in_requirements_file(script):
     ],
 )
 @pytest.mark.usefixtures("with_wheel")
-def test_relative_requirements_file(script, data, test_type, editable):
+def test_relative_requirements_file(
+    script: PipTestEnvironment, data: TestData, test_type: str, editable: bool
+) -> None:
     """
     Test installing from a requirements file with a relative path. For path
     URLs, use an egg= definition.
@@ -120,8 +128,8 @@ def test_relative_requirements_file(script, data, test_type, editable):
     package_folder = script.site_packages / "fspkg"
 
     # Compute relative install path to FSPkg from scratch path.
-    full_rel_path = Path(
-        os.path.relpath(data.packages.joinpath("FSPkg"), script.scratch_path)
+    full_rel_path = os.path.relpath(
+        data.packages.joinpath("FSPkg"), script.scratch_path
     )
     full_rel_url = "file:" + full_rel_path + "#egg=FSPkg"
     embedded_rel_path = script.scratch_path.joinpath(full_rel_path)
@@ -155,7 +163,7 @@ def test_relative_requirements_file(script, data, test_type, editable):
 @pytest.mark.network
 @need_svn
 @pytest.mark.usefixtures("with_wheel")
-def test_multiple_requirements_files(script, tmpdir):
+def test_multiple_requirements_files(script: PipTestEnvironment, tmpdir: Path) -> None:
     """
     Test installing from multiple nested requirements files.
 
@@ -182,7 +190,9 @@ def test_multiple_requirements_files(script, tmpdir):
     result.did_create(script.venv / "src" / "initools")
 
 
-def test_package_in_constraints_and_dependencies(script, data):
+def test_package_in_constraints_and_dependencies(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("constraints.txt").write_text(
         "TopoRequires2==0.0.1\nTopoRequires==0.0.1"
     )
@@ -198,7 +208,7 @@ def test_package_in_constraints_and_dependencies(script, data):
     assert "installed TopoRequires-0.0.1" in result.stdout
 
 
-def test_multiple_constraints_files(script, data):
+def test_multiple_constraints_files(script: PipTestEnvironment, data: TestData) -> None:
     script.scratch_path.joinpath("outer.txt").write_text("-c inner.txt")
     script.scratch_path.joinpath("inner.txt").write_text("Upper==1.0")
     result = script.pip(
@@ -214,7 +224,9 @@ def test_multiple_constraints_files(script, data):
 
 
 # FIXME: Unclear what this guarantee is for.
-def test_respect_order_in_requirements_file(script, data):
+def test_respect_order_in_requirements_file(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("frameworks-req.txt").write_text(
         textwrap.dedent(
             """\
@@ -247,7 +259,9 @@ def test_respect_order_in_requirements_file(script, data):
     ), 'Third download should be "simple" but was "{}"'.format(downloaded[2])
 
 
-def test_install_local_editable_with_extras(script, data):
+def test_install_local_editable_with_extras(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     res = script.pip_install_local(
         "-e", to_install + "[bar]", allow_stderr_warning=True
@@ -257,7 +271,7 @@ def test_install_local_editable_with_extras(script, data):
     res.did_create(script.site_packages / "simple")
 
 
-def test_install_collected_dependencies_first(script):
+def test_install_collected_dependencies_first(script: PipTestEnvironment) -> None:
     result = script.pip_install_local(
         "toporequires2",
     )
@@ -266,7 +280,7 @@ def test_install_collected_dependencies_first(script):
 
 
 @pytest.mark.network
-def test_install_local_editable_with_subdirectory(script):
+def test_install_local_editable_with_subdirectory(script: PipTestEnvironment) -> None:
     version_pkg_path = _create_test_package_with_subdirectory(script, "version_subdir")
     result = script.pip(
         "install",
@@ -280,7 +294,7 @@ def test_install_local_editable_with_subdirectory(script):
 
 
 @pytest.mark.network
-def test_install_local_with_subdirectory(script):
+def test_install_local_with_subdirectory(script: PipTestEnvironment) -> None:
     version_pkg_path = _create_test_package_with_subdirectory(script, "version_subdir")
     result = script.pip(
         "install",
@@ -294,7 +308,9 @@ def test_install_local_with_subdirectory(script):
 
 @pytest.mark.incompatible_with_test_venv
 @pytest.mark.usefixtures("with_wheel")
-def test_wheel_user_with_prefix_in_pydistutils_cfg(script, data):
+def test_wheel_user_with_prefix_in_pydistutils_cfg(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     if os.name == "posix":
         user_filename = ".pydistutils.cfg"
     else:
@@ -319,8 +335,9 @@ def test_wheel_user_with_prefix_in_pydistutils_cfg(script, data):
 
 
 def test_install_option_in_requirements_file_overrides_cli(
-    script, arg_recording_sdist_maker
-):
+    script: PipTestEnvironment,
+    arg_recording_sdist_maker: Callable[[str], ArgRecordingSdist],
+) -> None:
     simple_sdist = arg_recording_sdist_maker("simple")
 
     reqs_file = script.scratch_path.joinpath("reqs.txt")
@@ -340,7 +357,9 @@ def test_install_option_in_requirements_file_overrides_cli(
     assert simple_args.index("-O1") < simple_args.index("-O0")
 
 
-def test_constraints_not_installed_by_default(script, data):
+def test_constraints_not_installed_by_default(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("c.txt").write_text("requiresupper")
     result = script.pip(
         "install",
@@ -354,7 +373,9 @@ def test_constraints_not_installed_by_default(script, data):
     assert "requiresupper" not in result.stdout
 
 
-def test_constraints_only_causes_error(script, data):
+def test_constraints_only_causes_error(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("c.txt").write_text("requiresupper")
     result = script.pip(
         "install",
@@ -369,10 +390,10 @@ def test_constraints_only_causes_error(script, data):
 
 
 def test_constraints_local_editable_install_causes_error(
-    script,
-    data,
-    resolver_variant,
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    resolver_variant: ResolverVariant,
+) -> None:
     script.scratch_path.joinpath("constraints.txt").write_text("singlemodule==0.0.0")
     to_install = data.src.joinpath("singlemodule")
     result = script.pip(
@@ -394,7 +415,9 @@ def test_constraints_local_editable_install_causes_error(
 
 
 @pytest.mark.network
-def test_constraints_local_editable_install_pep518(script, data):
+def test_constraints_local_editable_install_pep518(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.src.joinpath("pep518-3.0")
 
     script.pip("download", "setuptools", "wheel", "-d", data.packages)
@@ -402,10 +425,10 @@ def test_constraints_local_editable_install_pep518(script, data):
 
 
 def test_constraints_local_install_causes_error(
-    script,
-    data,
-    resolver_variant,
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    resolver_variant: ResolverVariant,
+) -> None:
     script.scratch_path.joinpath("constraints.txt").write_text("singlemodule==0.0.0")
     to_install = data.src.joinpath("singlemodule")
     result = script.pip(
@@ -426,10 +449,10 @@ def test_constraints_local_install_causes_error(
 
 
 def test_constraints_constrain_to_local_editable(
-    script,
-    data,
-    resolver_variant,
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    resolver_variant: ResolverVariant,
+) -> None:
     to_install = data.src.joinpath("singlemodule")
     script.scratch_path.joinpath("constraints.txt").write_text(
         "-e {url}#egg=singlemodule".format(url=path_to_url(to_install))
@@ -451,7 +474,9 @@ def test_constraints_constrain_to_local_editable(
         assert "Running setup.py develop for singlemodule" in result.stdout
 
 
-def test_constraints_constrain_to_local(script, data, resolver_variant):
+def test_constraints_constrain_to_local(
+    script: PipTestEnvironment, data: TestData, resolver_variant: ResolverVariant
+) -> None:
     to_install = data.src.joinpath("singlemodule")
     script.scratch_path.joinpath("constraints.txt").write_text(
         "{url}#egg=singlemodule".format(url=path_to_url(to_install))
@@ -469,7 +494,9 @@ def test_constraints_constrain_to_local(script, data, resolver_variant):
     assert "Running setup.py install for singlemodule" in result.stdout
 
 
-def test_constrained_to_url_install_same_url(script, data):
+def test_constrained_to_url_install_same_url(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.src.joinpath("singlemodule")
     constraints = path_to_url(to_install) + "#egg=singlemodule"
     script.scratch_path.joinpath("constraints.txt").write_text(constraints)
@@ -487,7 +514,9 @@ def test_constrained_to_url_install_same_url(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_double_install_spurious_hash_mismatch(script, tmpdir, data):
+def test_double_install_spurious_hash_mismatch(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     """Make sure installing the same hashed sdist twice doesn't throw hash
     mismatch errors.
 
@@ -526,7 +555,9 @@ def test_double_install_spurious_hash_mismatch(script, tmpdir, data):
         assert "Successfully installed simple-1.0" in str(result)
 
 
-def test_install_with_extras_from_constraints(script, data, resolver_variant):
+def test_install_with_extras_from_constraints(
+    script: PipTestEnvironment, data: TestData, resolver_variant: ResolverVariant
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     script.scratch_path.joinpath("constraints.txt").write_text(
         "{url}#egg=LocalExtras[bar]".format(url=path_to_url(to_install))
@@ -544,12 +575,12 @@ def test_install_with_extras_from_constraints(script, data, resolver_variant):
         result.did_create(script.site_packages / "simple")
 
 
-def test_install_with_extras_from_install(script):
+def test_install_with_extras_from_install(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         name="LocalExtras",
         version="0.0.1",
-        extras={"bar": "simple", "baz": ["singlemodule"]},
+        extras={"bar": ["simple"], "baz": ["singlemodule"]},
     )
     script.scratch_path.joinpath("constraints.txt").write_text("LocalExtras")
     result = script.pip_install_local(
@@ -562,7 +593,9 @@ def test_install_with_extras_from_install(script):
     result.did_create(script.site_packages / "singlemodule.py")
 
 
-def test_install_with_extras_joined(script, data, resolver_variant):
+def test_install_with_extras_joined(
+    script: PipTestEnvironment, data: TestData, resolver_variant: ResolverVariant
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     script.scratch_path.joinpath("constraints.txt").write_text(
         "{url}#egg=LocalExtras[bar]".format(url=path_to_url(to_install))
@@ -581,7 +614,9 @@ def test_install_with_extras_joined(script, data, resolver_variant):
         result.did_create(script.site_packages / "singlemodule.py")
 
 
-def test_install_with_extras_editable_joined(script, data, resolver_variant):
+def test_install_with_extras_editable_joined(
+    script: PipTestEnvironment, data: TestData, resolver_variant: ResolverVariant
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     script.scratch_path.joinpath("constraints.txt").write_text(
         "-e {url}#egg=LocalExtras[bar]".format(url=path_to_url(to_install))
@@ -600,7 +635,9 @@ def test_install_with_extras_editable_joined(script, data, resolver_variant):
         result.did_create(script.site_packages / "singlemodule.py")
 
 
-def test_install_distribution_full_union(script, data):
+def test_install_distribution_full_union(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     result = script.pip_install_local(
         to_install, to_install + "[bar]", to_install + "[baz]"
@@ -610,7 +647,9 @@ def test_install_distribution_full_union(script, data):
     result.did_create(script.site_packages / "singlemodule.py")
 
 
-def test_install_distribution_duplicate_extras(script, data):
+def test_install_distribution_duplicate_extras(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     package_name = to_install + "[bar]"
     with pytest.raises(AssertionError):
@@ -620,10 +659,10 @@ def test_install_distribution_duplicate_extras(script, data):
 
 
 def test_install_distribution_union_with_constraints(
-    script,
-    data,
-    resolver_variant,
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    resolver_variant: ResolverVariant,
+) -> None:
     to_install = data.packages.joinpath("LocalExtras")
     script.scratch_path.joinpath("constraints.txt").write_text(f"{to_install}[bar]")
     result = script.pip_install_local(
@@ -642,10 +681,10 @@ def test_install_distribution_union_with_constraints(
 
 
 def test_install_distribution_union_with_versions(
-    script,
-    data,
-    resolver_variant,
-):
+    script: PipTestEnvironment,
+    data: TestData,
+    resolver_variant: ResolverVariant,
+) -> None:
     to_install_001 = data.packages.joinpath("LocalExtras")
     to_install_002 = data.packages.joinpath("LocalExtras-0.0.2")
     result = script.pip_install_local(
@@ -664,7 +703,9 @@ def test_install_distribution_union_with_versions(
 
 
 @pytest.mark.xfail
-def test_install_distribution_union_conflicting_extras(script, data):
+def test_install_distribution_union_conflicting_extras(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     # LocalExtras requires simple==1.0, LocalExtras[bar] requires simple==2.0;
     # without a resolver, pip does not detect the conflict between simple==1.0
     # and simple==2.0. Once a resolver is added, this conflict should be
@@ -677,7 +718,7 @@ def test_install_distribution_union_conflicting_extras(script, data):
     assert "Conflict" in result.stderr
 
 
-def test_install_unsupported_wheel_link_with_marker(script):
+def test_install_unsupported_wheel_link_with_marker(script: PipTestEnvironment) -> None:
     script.scratch_path.joinpath("with-marker.txt").write_text(
         textwrap.dedent(
             """\
@@ -697,7 +738,9 @@ def test_install_unsupported_wheel_link_with_marker(script):
     assert len(result.files_created) == 0
 
 
-def test_install_unsupported_wheel_file(script, data):
+def test_install_unsupported_wheel_file(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     # Trying to install a local wheel with an incompatible version/type
     # should fail.
     path = data.packages.joinpath("simple.dist-0.1-py1-none-invalid.whl")
@@ -716,7 +759,10 @@ def test_install_unsupported_wheel_file(script, data):
     assert len(result.files_created) == 0
 
 
-def test_install_options_local_to_package(script, arg_recording_sdist_maker):
+def test_install_options_local_to_package(
+    script: PipTestEnvironment,
+    arg_recording_sdist_maker: Callable[[str], ArgRecordingSdist],
+) -> None:
     """Make sure --install-options does not leak across packages.
 
     A requirements.txt file can have per-package --install-options; these
@@ -754,7 +800,7 @@ def test_install_options_local_to_package(script, arg_recording_sdist_maker):
     assert "-O0" not in simple2_args
 
 
-def test_location_related_install_option_fails(script):
+def test_location_related_install_option_fails(script: PipTestEnvironment) -> None:
     simple_sdist = create_basic_sdist_for_package(script, "simple", "0.1.0")
     reqs_file = script.scratch_path.joinpath("reqs.txt")
     reqs_file.write_text("simple --install-option='--home=/tmp'")
diff --git a/tests/functional/test_install_requested.py b/tests/functional/test_install_requested.py
index d7a6ea11082..0b5d5f18e75 100644
--- a/tests/functional/test_install_requested.py
+++ b/tests/functional/test_install_requested.py
@@ -1,14 +1,20 @@
 import pytest
 
+from tests.lib import PipTestEnvironment, TestData, TestPipResult
 
-def _assert_requested_present(script, result, name, version):
+
+def _assert_requested_present(
+    script: PipTestEnvironment, result: TestPipResult, name: str, version: str
+) -> None:
     dist_info = script.site_packages / name + "-" + version + ".dist-info"
     requested = dist_info / "REQUESTED"
     assert dist_info in result.files_created
     assert requested in result.files_created
 
 
-def _assert_requested_absent(script, result, name, version):
+def _assert_requested_absent(
+    script: PipTestEnvironment, result: TestPipResult, name: str, version: str
+) -> None:
     dist_info = script.site_packages / name + "-" + version + ".dist-info"
     requested = dist_info / "REQUESTED"
     assert dist_info in result.files_created
@@ -16,7 +22,7 @@ def _assert_requested_absent(script, result, name, version):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_requested_basic(script, data):
+def test_install_requested_basic(script: PipTestEnvironment, data: TestData) -> None:
     result = script.pip(
         "install", "--no-index", "-f", data.find_links, "require_simple"
     )
@@ -26,7 +32,9 @@ def test_install_requested_basic(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_requested_requirements(script, data):
+def test_install_requested_requirements(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("requirements.txt").write_text("require_simple\n")
     result = script.pip(
         "install",
@@ -41,7 +49,9 @@ def test_install_requested_requirements(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_requested_dep_in_requirements(script, data):
+def test_install_requested_dep_in_requirements(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("requirements.txt").write_text(
         "require_simple\nsimple<3\n"
     )
@@ -59,7 +69,9 @@ def test_install_requested_dep_in_requirements(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_requested_reqs_and_constraints(script, data):
+def test_install_requested_reqs_and_constraints(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("requirements.txt").write_text("require_simple\n")
     script.scratch_path.joinpath("constraints.txt").write_text("simple<3\n")
     result = script.pip(
@@ -78,7 +90,9 @@ def test_install_requested_reqs_and_constraints(script, data):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_requested_in_reqs_and_constraints(script, data):
+def test_install_requested_in_reqs_and_constraints(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.scratch_path.joinpath("requirements.txt").write_text(
         "require_simple\nsimple\n"
     )
diff --git a/tests/functional/test_install_upgrade.py b/tests/functional/test_install_upgrade.py
index d325a3d600e..f626393ce60 100644
--- a/tests/functional/test_install_upgrade.py
+++ b/tests/functional/test_install_upgrade.py
@@ -5,13 +5,14 @@
 import pytest
 
 from tests.lib import pyversion  # noqa: F401
-from tests.lib import assert_all_changes
+from tests.lib import PipTestEnvironment, ResolverVariant, TestData, assert_all_changes
 from tests.lib.local_repos import local_checkout
+from tests.lib.path import Path
 from tests.lib.wheel import make_wheel
 
 
 @pytest.mark.network
-def test_no_upgrade_unless_requested(script):
+def test_no_upgrade_unless_requested(script: PipTestEnvironment) -> None:
     """
     No upgrade if not specifically requested.
 
@@ -23,7 +24,7 @@ def test_no_upgrade_unless_requested(script):
     ), "pip install INITools upgraded when it should not have"
 
 
-def test_invalid_upgrade_strategy_causes_error(script):
+def test_invalid_upgrade_strategy_causes_error(script: PipTestEnvironment) -> None:
     """
     It errors out when the upgrade-strategy is an invalid/unrecognised one
 
@@ -37,7 +38,9 @@ def test_invalid_upgrade_strategy_causes_error(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_only_if_needed_does_not_upgrade_deps_when_satisfied(script, resolver_variant):
+def test_only_if_needed_does_not_upgrade_deps_when_satisfied(
+    script: PipTestEnvironment, resolver_variant: ResolverVariant
+) -> None:
     """
     It doesn't upgrade a dependency if it already satisfies the requirements.
 
@@ -63,7 +66,9 @@ def test_only_if_needed_does_not_upgrade_deps_when_satisfied(script, resolver_va
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_only_if_needed_does_upgrade_deps_when_no_longer_satisfied(script):
+def test_only_if_needed_does_upgrade_deps_when_no_longer_satisfied(
+    script: PipTestEnvironment,
+) -> None:
     """
     It does upgrade a dependency if it no longer satisfies the requirements.
 
@@ -83,7 +88,9 @@ def test_only_if_needed_does_upgrade_deps_when_no_longer_satisfied(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_eager_does_upgrade_dependencies_when_currently_satisfied(script):
+def test_eager_does_upgrade_dependencies_when_currently_satisfied(
+    script: PipTestEnvironment,
+) -> None:
     """
     It does upgrade a dependency even if it already satisfies the requirements.
 
@@ -102,7 +109,9 @@ def test_eager_does_upgrade_dependencies_when_currently_satisfied(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_eager_does_upgrade_dependencies_when_no_longer_satisfied(script):
+def test_eager_does_upgrade_dependencies_when_no_longer_satisfied(
+    script: PipTestEnvironment,
+) -> None:
     """
     It does upgrade a dependency if it no longer satisfies the requirements.
 
@@ -126,7 +135,7 @@ def test_eager_does_upgrade_dependencies_when_no_longer_satisfied(script):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_upgrade_to_specific_version(script):
+def test_upgrade_to_specific_version(script: PipTestEnvironment) -> None:
     """
     It does upgrade to specific version requested.
 
@@ -140,7 +149,7 @@ def test_upgrade_to_specific_version(script):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_upgrade_if_requested(script):
+def test_upgrade_if_requested(script: PipTestEnvironment) -> None:
     """
     And it does upgrade if requested.
 
@@ -151,7 +160,9 @@ def test_upgrade_if_requested(script):
     result.did_not_create(script.site_packages / "INITools-0.1.dist-info")
 
 
-def test_upgrade_with_newest_already_installed(script, data, resolver_variant):
+def test_upgrade_with_newest_already_installed(
+    script: PipTestEnvironment, data: TestData, resolver_variant: ResolverVariant
+) -> None:
     """
     If the newest version of a package is already installed, the package should
     not be reinstalled and the user should be informed.
@@ -169,7 +180,7 @@ def test_upgrade_with_newest_already_installed(script, data, resolver_variant):
 
 
 @pytest.mark.network
-def test_upgrade_force_reinstall_newest(script):
+def test_upgrade_force_reinstall_newest(script: PipTestEnvironment) -> None:
     """
     Force reinstallation of a package even if it is already at its newest
     version if --force-reinstall is supplied.
@@ -183,7 +194,7 @@ def test_upgrade_force_reinstall_newest(script):
 
 
 @pytest.mark.network
-def test_uninstall_before_upgrade(script):
+def test_uninstall_before_upgrade(script: PipTestEnvironment) -> None:
     """
     Automatic uninstall-before-upgrade.
 
@@ -197,7 +208,7 @@ def test_uninstall_before_upgrade(script):
 
 
 @pytest.mark.network
-def test_uninstall_before_upgrade_from_url(script):
+def test_uninstall_before_upgrade_from_url(script: PipTestEnvironment) -> None:
     """
     Automatic uninstall-before-upgrade from URL.
 
@@ -215,7 +226,7 @@ def test_uninstall_before_upgrade_from_url(script):
 
 
 @pytest.mark.network
-def test_upgrade_to_same_version_from_url(script):
+def test_upgrade_to_same_version_from_url(script: PipTestEnvironment) -> None:
     """
     When installing from a URL the same version that is already installed, no
     need to uninstall and reinstall if --upgrade is not specified.
@@ -236,7 +247,7 @@ def test_upgrade_to_same_version_from_url(script):
 
 
 @pytest.mark.network
-def test_upgrade_from_reqs_file(script):
+def test_upgrade_from_reqs_file(script: PipTestEnvironment) -> None:
     """
     Upgrade from a requirements file.
 
@@ -271,7 +282,7 @@ def test_upgrade_from_reqs_file(script):
     )
 
 
-def test_uninstall_rollback(script, data):
+def test_uninstall_rollback(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test uninstall-rollback (using test package with a setup.py
     crafted to fail on install).
@@ -301,7 +312,7 @@ def test_uninstall_rollback(script, data):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_should_not_install_always_from_cache(script):
+def test_should_not_install_always_from_cache(script: PipTestEnvironment) -> None:
     """
     If there is an old cached package, pip should download the newer version
     Related to issue #175
@@ -315,7 +326,7 @@ def test_should_not_install_always_from_cache(script):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_with_ignoreinstalled_requested(script):
+def test_install_with_ignoreinstalled_requested(script: PipTestEnvironment) -> None:
     """
     Test old conflicting package is completely ignored
     """
@@ -328,7 +339,9 @@ def test_install_with_ignoreinstalled_requested(script):
 
 
 @pytest.mark.network
-def test_upgrade_vcs_req_with_no_dists_found(script, tmpdir):
+def test_upgrade_vcs_req_with_no_dists_found(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """It can upgrade a VCS requirement that has no distributions otherwise."""
     req = "{checkout}#egg=pip-test-package".format(
         checkout=local_checkout(
@@ -342,7 +355,7 @@ def test_upgrade_vcs_req_with_no_dists_found(script, tmpdir):
 
 
 @pytest.mark.network
-def test_upgrade_vcs_req_with_dist_found(script):
+def test_upgrade_vcs_req_with_dist_found(script: PipTestEnvironment) -> None:
     """It can upgrade a VCS requirement that has distributions on the index."""
     # TODO(pnasrat) Using local_checkout fails on windows - oddness with the
     # test path urls/git.
@@ -366,7 +379,9 @@ def test_upgrade_vcs_req_with_dist_found(script):
         )
     ),
 )
-def test_install_find_existing_package_canonicalize(script, req1, req2):
+def test_install_find_existing_package_canonicalize(
+    script: PipTestEnvironment, req1: str, req2: str
+) -> None:
     """Ensure an already-installed dist is found no matter how the dist name
     was normalized on installation. (pypa/pip#8645)
     """
diff --git a/tests/functional/test_install_user.py b/tests/functional/test_install_user.py
index 3cf8b1e295b..59624c186bc 100644
--- a/tests/functional/test_install_user.py
+++ b/tests/functional/test_install_user.py
@@ -7,11 +7,13 @@
 import pytest
 
 from tests.lib import pyversion  # noqa: F401
-from tests.lib import need_svn
+from tests.lib import PipTestEnvironment, TestData, need_svn
 from tests.lib.local_repos import local_checkout
+from tests.lib.path import Path
+from tests.lib.venv import VirtualEnvironment
 
 
-def _patch_dist_in_site_packages(virtualenv):
+def _patch_dist_in_site_packages(virtualenv: VirtualEnvironment) -> None:
     # Since the tests are run from a virtualenv, and to avoid the "Will not
     # install to the usersite because it will lack sys.path precedence..."
     # error: Monkey patch `pip._internal.req.req_install.dist_in_site_packages`
@@ -33,7 +35,9 @@ def dist_in_site_packages(dist):
 class Tests_UserSite:
     @pytest.mark.network
     @pytest.mark.incompatible_with_test_venv
-    def test_reset_env_system_site_packages_usersite(self, script):
+    def test_reset_env_system_site_packages_usersite(
+        self, script: PipTestEnvironment
+    ) -> None:
         """
         Check user site works as expected.
         """
@@ -51,7 +55,9 @@ def test_reset_env_system_site_packages_usersite(self, script):
     @pytest.mark.network
     @need_svn
     @pytest.mark.incompatible_with_test_venv
-    def test_install_subversion_usersite_editable_with_distribute(self, script, tmpdir):
+    def test_install_subversion_usersite_editable_with_distribute(
+        self, script: PipTestEnvironment, tmpdir: Path
+    ) -> None:
         """
         Test installing current directory ('.') into usersite after installing
         distribute
@@ -70,7 +76,9 @@ def test_install_subversion_usersite_editable_with_distribute(self, script, tmpd
 
     @pytest.mark.incompatible_with_test_venv
     @pytest.mark.usefixtures("with_wheel")
-    def test_install_from_current_directory_into_usersite(self, script, data):
+    def test_install_from_current_directory_into_usersite(
+        self, script: PipTestEnvironment, data: TestData
+    ) -> None:
         """
         Test installing current directory ('.') into usersite
         """
@@ -89,7 +97,9 @@ def test_install_from_current_directory_into_usersite(self, script, data):
         dist_info_folder = script.user_site / "FSPkg-0.1.dev0.dist-info"
         result.did_create(dist_info_folder)
 
-    def test_install_user_venv_nositepkgs_fails(self, virtualenv, script, data):
+    def test_install_user_venv_nositepkgs_fails(
+        self, virtualenv: VirtualEnvironment, script: PipTestEnvironment, data: TestData
+    ) -> None:
         """
         user install in virtualenv (with no system packages) fails with message
         """
@@ -111,7 +121,9 @@ def test_install_user_venv_nositepkgs_fails(self, virtualenv, script, data):
 
     @pytest.mark.network
     @pytest.mark.incompatible_with_test_venv
-    def test_install_user_conflict_in_usersite(self, script):
+    def test_install_user_conflict_in_usersite(
+        self, script: PipTestEnvironment
+    ) -> None:
         """
         Test user install with conflict in usersite updates usersite.
         """
@@ -135,7 +147,9 @@ def test_install_user_conflict_in_usersite(self, script):
 
     @pytest.mark.network
     @pytest.mark.incompatible_with_test_venv
-    def test_install_user_conflict_in_globalsite(self, virtualenv, script):
+    def test_install_user_conflict_in_globalsite(
+        self, virtualenv: VirtualEnvironment, script: PipTestEnvironment
+    ) -> None:
         """
         Test user install with conflict in global site ignores site and
         installs to usersite
@@ -165,7 +179,9 @@ def test_install_user_conflict_in_globalsite(self, virtualenv, script):
 
     @pytest.mark.network
     @pytest.mark.incompatible_with_test_venv
-    def test_upgrade_user_conflict_in_globalsite(self, virtualenv, script):
+    def test_upgrade_user_conflict_in_globalsite(
+        self, virtualenv: VirtualEnvironment, script: PipTestEnvironment
+    ) -> None:
         """
         Test user install/upgrade with conflict in global site ignores site and
         installs to usersite
@@ -196,7 +212,9 @@ def test_upgrade_user_conflict_in_globalsite(self, virtualenv, script):
 
     @pytest.mark.network
     @pytest.mark.incompatible_with_test_venv
-    def test_install_user_conflict_in_globalsite_and_usersite(self, virtualenv, script):
+    def test_install_user_conflict_in_globalsite_and_usersite(
+        self, virtualenv: VirtualEnvironment, script: PipTestEnvironment
+    ) -> None:
         """
         Test user install with conflict in globalsite and usersite ignores
         global site and updates usersite.
@@ -233,7 +251,9 @@ def test_install_user_conflict_in_globalsite_and_usersite(self, virtualenv, scri
 
     @pytest.mark.network
     @pytest.mark.incompatible_with_test_venv
-    def test_install_user_in_global_virtualenv_with_conflict_fails(self, script):
+    def test_install_user_in_global_virtualenv_with_conflict_fails(
+        self, script: PipTestEnvironment
+    ) -> None:
         """
         Test user install in --system-site-packages virtualenv with conflict in
         site fails.
diff --git a/tests/functional/test_install_vcs_git.py b/tests/functional/test_install_vcs_git.py
index b7a288d7085..3836a251e2e 100644
--- a/tests/functional/test_install_vcs_git.py
+++ b/tests/functional/test_install_vcs_git.py
@@ -1,8 +1,11 @@
+from typing import Optional
+
 import pytest
 
 from pip._internal.utils.urls import path_to_url
 from tests.lib import pyversion  # noqa: F401
 from tests.lib import (
+    PipTestEnvironment,
     _change_test_package_version,
     _create_test_package,
     _test_path_to_file_url,
@@ -13,16 +16,17 @@
     _pull_in_submodule_changes_to_module,
 )
 from tests.lib.local_repos import local_checkout
+from tests.lib.path import Path
 
 
-def _get_editable_repo_dir(script, package_name):
+def _get_editable_repo_dir(script: PipTestEnvironment, package_name: str) -> Path:
     """
     Return the repository directory for an editable install.
     """
     return script.venv_path / "src" / package_name
 
 
-def _get_editable_branch(script, package_name):
+def _get_editable_branch(script: PipTestEnvironment, package_name: str) -> str:
     """
     Return the current branch of an editable install.
     """
@@ -31,14 +35,22 @@ def _get_editable_branch(script, package_name):
     return result.stdout.strip()
 
 
-def _get_branch_remote(script, package_name, branch):
+def _get_branch_remote(
+    script: PipTestEnvironment, package_name: str, branch: str
+) -> str:
     """ """
     repo_dir = _get_editable_repo_dir(script, package_name)
     result = script.run("git", "config", f"branch.{branch}.remote", cwd=repo_dir)
     return result.stdout.strip()
 
 
-def _github_checkout(url_path, temp_dir, rev=None, egg=None, scheme=None):
+def _github_checkout(
+    url_path: str,
+    temp_dir: Path,
+    rev: Optional[str] = None,
+    egg: Optional[str] = None,
+    scheme: Optional[str] = None,
+) -> str:
     """
     Call local_checkout() with a GitHub URL, and return the resulting URL.
 
@@ -62,7 +74,9 @@ def _github_checkout(url_path, temp_dir, rev=None, egg=None, scheme=None):
     return local_url
 
 
-def _make_version_pkg_url(path, rev=None, name="version_pkg"):
+def _make_version_pkg_url(
+    path: Path, rev: Optional[str] = None, name: str = "version_pkg"
+) -> str:
     """
     Return a "git+file://" URL to the version_pkg test package.
 
@@ -78,7 +92,12 @@ def _make_version_pkg_url(path, rev=None, name="version_pkg"):
     return url
 
 
-def _install_version_pkg_only(script, path, rev=None, expect_stderr=False):
+def _install_version_pkg_only(
+    script: PipTestEnvironment,
+    path: Path,
+    rev: Optional[str] = None,
+    expect_stderr: bool = False,
+) -> None:
     """
     Install the version_pkg package in editable mode (without returning
     the version).
@@ -92,7 +111,12 @@ def _install_version_pkg_only(script, path, rev=None, expect_stderr=False):
     script.pip("install", "-e", version_pkg_url, expect_stderr=expect_stderr)
 
 
-def _install_version_pkg(script, path, rev=None, expect_stderr=False):
+def _install_version_pkg(
+    script: PipTestEnvironment,
+    path: Path,
+    rev: Optional[str] = None,
+    expect_stderr: bool = False,
+) -> str:
     """
     Install the version_pkg package in editable mode, and return the version
     installed.
@@ -114,7 +138,7 @@ def _install_version_pkg(script, path, rev=None, expect_stderr=False):
     return version
 
 
-def test_git_install_again_after_changes(script):
+def test_git_install_again_after_changes(script: PipTestEnvironment) -> None:
     """
     Test installing a repository a second time without specifying a revision,
     and after updates to the remote repository.
@@ -132,7 +156,9 @@ def test_git_install_again_after_changes(script):
     assert version == "some different version"
 
 
-def test_git_install_branch_again_after_branch_changes(script):
+def test_git_install_branch_again_after_branch_changes(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test installing a branch again after the branch is updated in the remote
     repository.
@@ -147,7 +173,9 @@ def test_git_install_branch_again_after_branch_changes(script):
 
 
 @pytest.mark.network
-def test_install_editable_from_git_with_https(script, tmpdir):
+def test_install_editable_from_git_with_https(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test cloning from Git with https.
     """
@@ -159,7 +187,7 @@ def test_install_editable_from_git_with_https(script, tmpdir):
 
 @pytest.mark.network
 @pytest.mark.usefixtures("with_wheel")
-def test_install_noneditable_git(script):
+def test_install_noneditable_git(script: PipTestEnvironment) -> None:
     """
     Test installing from a non-editable git URL with a given tag.
     """
@@ -173,7 +201,7 @@ def test_install_noneditable_git(script):
     result.did_create(dist_info_folder)
 
 
-def test_git_with_sha1_revisions(script):
+def test_git_with_sha1_revisions(script: PipTestEnvironment) -> None:
     """
     Git backend should be able to install from SHA1 revisions
     """
@@ -189,7 +217,7 @@ def test_git_with_sha1_revisions(script):
     assert "0.1" == version
 
 
-def test_git_with_short_sha1_revisions(script):
+def test_git_with_short_sha1_revisions(script: PipTestEnvironment) -> None:
     """
     Git backend should be able to install from SHA1 revisions
     """
@@ -205,7 +233,7 @@ def test_git_with_short_sha1_revisions(script):
     assert "0.1" == version
 
 
-def test_git_with_branch_name_as_revision(script):
+def test_git_with_branch_name_as_revision(script: PipTestEnvironment) -> None:
     """
     Git backend should be able to install from branch names
     """
@@ -217,7 +245,7 @@ def test_git_with_branch_name_as_revision(script):
     assert "some different version" == version
 
 
-def test_git_with_tag_name_as_revision(script):
+def test_git_with_tag_name_as_revision(script: PipTestEnvironment) -> None:
     """
     Git backend should be able to install from tag names
     """
@@ -228,14 +256,14 @@ def test_git_with_tag_name_as_revision(script):
     assert "0.1" == version
 
 
-def _add_ref(script, path, ref):
+def _add_ref(script: PipTestEnvironment, path: Path, ref: str) -> None:
     """
     Add a new ref to a repository at the given path.
     """
     script.run("git", "update-ref", ref, "HEAD", cwd=path)
 
 
-def test_git_install_ref(script):
+def test_git_install_ref(script: PipTestEnvironment) -> None:
     """
     The Git backend should be able to install a ref with the first install.
     """
@@ -251,7 +279,7 @@ def test_git_install_ref(script):
     assert "0.1" == version
 
 
-def test_git_install_then_install_ref(script):
+def test_git_install_then_install_ref(script: PipTestEnvironment) -> None:
     """
     The Git backend should be able to install a ref after a package has
     already been installed.
@@ -287,7 +315,9 @@ def test_git_install_then_install_ref(script):
         ),
     ],
 )
-def test_install_git_logs_commit_sha(script, rev, expected_sha, tmpdir):
+def test_install_git_logs_commit_sha(
+    script: PipTestEnvironment, rev: str, expected_sha: str, tmpdir: Path
+) -> None:
     """
     Test installing from a git repository logs a commit SHA.
     """
@@ -300,7 +330,7 @@ def test_install_git_logs_commit_sha(script, rev, expected_sha, tmpdir):
 
 
 @pytest.mark.network
-def test_git_with_tag_name_and_update(script, tmpdir):
+def test_git_with_tag_name_and_update(script: PipTestEnvironment, tmpdir: Path) -> None:
     """
     Test cloning a git repository and updating to a different version.
     """
@@ -322,7 +352,9 @@ def test_git_with_tag_name_and_update(script, tmpdir):
 
 
 @pytest.mark.network
-def test_git_branch_should_not_be_changed(script, tmpdir):
+def test_git_branch_should_not_be_changed(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Editable installations should not change branch
     related to issue #32 and #161
@@ -335,7 +367,9 @@ def test_git_branch_should_not_be_changed(script, tmpdir):
 
 
 @pytest.mark.network
-def test_git_with_non_editable_unpacking(script, tmpdir):
+def test_git_with_non_editable_unpacking(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test cloning a git repository from a non-editable URL with a given tag.
     """
@@ -351,7 +385,9 @@ def test_git_with_non_editable_unpacking(script, tmpdir):
 
 
 @pytest.mark.network
-def test_git_with_editable_where_egg_contains_dev_string(script, tmpdir):
+def test_git_with_editable_where_egg_contains_dev_string(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test cloning a git repository from an editable url which contains "dev"
     string
@@ -368,7 +404,9 @@ def test_git_with_editable_where_egg_contains_dev_string(script, tmpdir):
 
 
 @pytest.mark.network
-def test_git_with_non_editable_where_egg_contains_dev_string(script, tmpdir):
+def test_git_with_non_editable_where_egg_contains_dev_string(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test cloning a git repository from a non-editable url which contains "dev"
     string
@@ -385,7 +423,7 @@ def test_git_with_non_editable_where_egg_contains_dev_string(script, tmpdir):
     result.did_create(devserver_folder)
 
 
-def test_git_with_ambiguous_revs(script):
+def test_git_with_ambiguous_revs(script: PipTestEnvironment) -> None:
     """
     Test git with two "names" (tag/branch) pointing to the same commit
     """
@@ -399,7 +437,7 @@ def test_git_with_ambiguous_revs(script):
     result.assert_installed("version-pkg", with_files=[".git"])
 
 
-def test_editable__no_revision(script):
+def test_editable__no_revision(script: PipTestEnvironment) -> None:
     """
     Test a basic install in editable mode specifying no revision.
     """
@@ -413,7 +451,7 @@ def test_editable__no_revision(script):
     assert remote == "origin"
 
 
-def test_editable__branch_with_sha_same_as_default(script):
+def test_editable__branch_with_sha_same_as_default(script: PipTestEnvironment) -> None:
     """
     Test installing in editable mode a branch whose sha matches the sha
     of the default branch, but is different from the default branch.
@@ -430,7 +468,9 @@ def test_editable__branch_with_sha_same_as_default(script):
     assert remote == "origin"
 
 
-def test_editable__branch_with_sha_different_from_default(script):
+def test_editable__branch_with_sha_different_from_default(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test installing in editable mode a branch whose sha is different from
     the sha of the default branch.
@@ -451,7 +491,7 @@ def test_editable__branch_with_sha_different_from_default(script):
     assert remote == "origin"
 
 
-def test_editable__non_master_default_branch(script):
+def test_editable__non_master_default_branch(script: PipTestEnvironment) -> None:
     """
     Test the branch you get after an editable install from a remote repo
     with a non-master default branch.
@@ -466,7 +506,9 @@ def test_editable__non_master_default_branch(script):
     assert branch == "release"
 
 
-def test_reinstalling_works_with_editable_non_master_branch(script):
+def test_reinstalling_works_with_editable_non_master_branch(
+    script: PipTestEnvironment,
+) -> None:
     """
     Reinstalling an editable installation should not assume that the "master"
     branch exists. See https://github.com/pypa/pip/issues/4448.
@@ -486,7 +528,7 @@ def test_reinstalling_works_with_editable_non_master_branch(script):
 
 # TODO(pnasrat) fix all helpers to do right things with paths on windows.
 @pytest.mark.skipif("sys.platform == 'win32'")
-def test_check_submodule_addition(script):
+def test_check_submodule_addition(script: PipTestEnvironment) -> None:
     """
     Submodules are pulled in on install and updated on upgrade.
     """
@@ -518,7 +560,7 @@ def test_check_submodule_addition(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_git_branch_not_cached(script):
+def test_install_git_branch_not_cached(script: PipTestEnvironment) -> None:
     """
     Installing git urls with a branch revision does not cause wheel caching.
     """
@@ -534,7 +576,7 @@ def test_install_git_branch_not_cached(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_git_sha_cached(script):
+def test_install_git_sha_cached(script: PipTestEnvironment) -> None:
     """
     Installing git urls with a sha revision does cause wheel caching.
     """
diff --git a/tests/functional/test_install_wheel.py b/tests/functional/test_install_wheel.py
index c7045a9dc5b..86c5e5fbeb2 100644
--- a/tests/functional/test_install_wheel.py
+++ b/tests/functional/test_install_wheel.py
@@ -3,22 +3,25 @@
 import glob
 import os
 import shutil
+from typing import Any
 
 import pytest
 
-from tests.lib import create_basic_wheel_for_package
+from tests.lib import PipTestEnvironment, TestData, create_basic_wheel_for_package
 from tests.lib.path import Path
-from tests.lib.wheel import make_wheel
+from tests.lib.wheel import WheelBuilder, make_wheel
 
 
 # assert_installed expects a package subdirectory, so give it to them
-def make_wheel_with_file(name, version, **kwargs):
+def make_wheel_with_file(name: str, version: str, **kwargs: Any) -> WheelBuilder:
     extra_files = kwargs.setdefault("extra_files", {})
     extra_files[f"{name}/__init__.py"] = "# example"
     return make_wheel(name=name, version=version, **kwargs)
 
 
-def test_install_from_future_wheel_version(script, tmpdir):
+def test_install_from_future_wheel_version(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test installing a wheel with a WHEEL metadata version that is:
     - a major version ahead of what we expect (not ok), and
@@ -52,7 +55,9 @@ def test_install_from_future_wheel_version(script, tmpdir):
         "corruptwheel-1.0-py2.py3-none-any.whl",
     ],
 )
-def test_install_from_broken_wheel(script, data, wheel_name):
+def test_install_from_broken_wheel(
+    script: PipTestEnvironment, data: TestData, wheel_name: str
+) -> None:
     """
     Test that installing a broken wheel fails properly
     """
@@ -64,7 +69,9 @@ def test_install_from_broken_wheel(script, data, wheel_name):
         result.assert_installed("futurewheel", without_egg_link=True, editable=False)
 
 
-def test_basic_install_from_wheel(script, shared_data, tmpdir):
+def test_basic_install_from_wheel(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing from a wheel (that has a script)
     """
@@ -82,7 +89,9 @@ def test_basic_install_from_wheel(script, shared_data, tmpdir):
     result.did_create(script_file)
 
 
-def test_basic_install_from_wheel_with_extras(script, shared_data, tmpdir):
+def test_basic_install_from_wheel_with_extras(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing from a wheel with extras.
     """
@@ -101,7 +110,9 @@ def test_basic_install_from_wheel_with_extras(script, shared_data, tmpdir):
     result.did_create(dist_info_folder)
 
 
-def test_basic_install_from_wheel_file(script, data):
+def test_basic_install_from_wheel_file(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing directly from a wheel file.
     """
@@ -120,7 +131,9 @@ def test_basic_install_from_wheel_file(script, data):
 
 # Installation seems to work, but scripttest fails to check.
 # I really don't care now since we're desupporting it soon anyway.
-def test_basic_install_from_unicode_wheel(script, data):
+def test_basic_install_from_unicode_wheel(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test installing from a wheel (that has a script)
     """
@@ -150,7 +163,9 @@ def test_basic_install_from_unicode_wheel(script, data):
     result.did_create(file2)
 
 
-def get_header_scheme_path_for_script(script, dist_name):
+def get_header_scheme_path_for_script(
+    script: PipTestEnvironment, dist_name: str
+) -> Path:
     command = (
         "from pip._internal.locations import get_scheme;"
         "scheme = get_scheme({!r});"
@@ -160,7 +175,7 @@ def get_header_scheme_path_for_script(script, dist_name):
     return Path(result.strip())
 
 
-def test_install_from_wheel_with_headers(script):
+def test_install_from_wheel_with_headers(script: PipTestEnvironment) -> None:
     """
     Test installing from a wheel file with headers
     """
@@ -180,7 +195,9 @@ def test_install_from_wheel_with_headers(script):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_wheel_with_target(script, shared_data, tmpdir):
+def test_install_wheel_with_target(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing a wheel using pip install --target
     """
@@ -199,7 +216,9 @@ def test_install_wheel_with_target(script, shared_data, tmpdir):
 
 
 @pytest.mark.usefixtures("with_wheel")
-def test_install_wheel_with_target_and_data_files(script, data):
+def test_install_wheel_with_target_and_data_files(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test for issue #4092. It will be checked that a data_files specification in
     setup.py is handled correctly when a wheel is installed with the --target
@@ -227,7 +246,9 @@ def test_install_wheel_with_target_and_data_files(script, data):
     result.did_not_create(project_path / "lib" / "python")
 
 
-def test_install_wheel_with_root(script, shared_data, tmpdir):
+def test_install_wheel_with_root(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing a wheel using pip install --root
     """
@@ -245,7 +266,9 @@ def test_install_wheel_with_root(script, shared_data, tmpdir):
     result.did_create(Path("scratch") / "root")
 
 
-def test_install_wheel_with_prefix(script, shared_data, tmpdir):
+def test_install_wheel_with_prefix(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing a wheel using pip install --prefix
     """
@@ -264,7 +287,9 @@ def test_install_wheel_with_prefix(script, shared_data, tmpdir):
     result.did_create(lib)
 
 
-def test_install_from_wheel_installs_deps(script, data, tmpdir):
+def test_install_from_wheel_installs_deps(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test can install dependencies of wheels
     """
@@ -281,7 +306,9 @@ def test_install_from_wheel_installs_deps(script, data, tmpdir):
     result.assert_installed("source", editable=False)
 
 
-def test_install_from_wheel_no_deps(script, data, tmpdir):
+def test_install_from_wheel_no_deps(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test --no-deps works with wheel installs
     """
@@ -300,7 +327,9 @@ def test_install_from_wheel_no_deps(script, data, tmpdir):
     result.did_not_create(pkg_folder)
 
 
-def test_wheel_record_lines_in_deterministic_order(script, data):
+def test_wheel_record_lines_in_deterministic_order(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     to_install = data.packages.joinpath("simplewheel-1.0-py2.py3-none-any.whl")
     result = script.pip("install", to_install)
 
@@ -315,7 +344,9 @@ def test_wheel_record_lines_in_deterministic_order(script, data):
     assert record_lines == sorted(record_lines)
 
 
-def test_wheel_record_lines_have_hash_for_data_files(script):
+def test_wheel_record_lines_have_hash_for_data_files(
+    script: PipTestEnvironment,
+) -> None:
     package = make_wheel(
         "simple",
         "0.1.0",
@@ -336,7 +367,9 @@ def test_wheel_record_lines_have_hash_for_data_files(script):
 
 @pytest.mark.incompatible_with_test_venv
 @pytest.mark.usefixtures("with_wheel")
-def test_install_user_wheel(script, shared_data, tmpdir):
+def test_install_user_wheel(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test user install from wheel (that has a script)
     """
@@ -355,7 +388,9 @@ def test_install_user_wheel(script, shared_data, tmpdir):
     result.did_create(script_file)
 
 
-def test_install_from_wheel_gen_entrypoint(script, shared_data, tmpdir):
+def test_install_from_wheel_gen_entrypoint(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing scripts (entry points are generated)
     """
@@ -380,7 +415,9 @@ def test_install_from_wheel_gen_entrypoint(script, shared_data, tmpdir):
         assert bool(os.access(script.base_path / wrapper_file, os.X_OK))
 
 
-def test_install_from_wheel_gen_uppercase_entrypoint(script, shared_data, tmpdir):
+def test_install_from_wheel_gen_uppercase_entrypoint(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing scripts with uppercase letters in entry point names
     """
@@ -406,7 +443,7 @@ def test_install_from_wheel_gen_uppercase_entrypoint(script, shared_data, tmpdir
         assert bool(os.access(script.base_path / wrapper_file, os.X_OK))
 
 
-def test_install_from_wheel_gen_unicode_entrypoint(script):
+def test_install_from_wheel_gen_unicode_entrypoint(script: PipTestEnvironment) -> None:
     make_wheel(
         "script_wheel_unicode",
         "1.0",
@@ -426,7 +463,9 @@ def test_install_from_wheel_gen_unicode_entrypoint(script):
         result.did_create(script.bin.joinpath("進入點"))
 
 
-def test_install_from_wheel_with_legacy(script, shared_data, tmpdir):
+def test_install_from_wheel_with_legacy(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing scripts (legacy scripts are preserved)
     """
@@ -449,7 +488,9 @@ def test_install_from_wheel_with_legacy(script, shared_data, tmpdir):
     result.did_create(legacy_file2)
 
 
-def test_install_from_wheel_no_setuptools_entrypoint(script, shared_data, tmpdir):
+def test_install_from_wheel_no_setuptools_entrypoint(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test that when we generate scripts, any existing setuptools wrappers in
     the wheel are skipped.
@@ -477,7 +518,9 @@ def test_install_from_wheel_no_setuptools_entrypoint(script, shared_data, tmpdir
     result.did_not_create(wrapper_helper)
 
 
-def test_skipping_setuptools_doesnt_skip_legacy(script, shared_data, tmpdir):
+def test_skipping_setuptools_doesnt_skip_legacy(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing scripts (legacy scripts are preserved even when we skip
     setuptools wrappers)
@@ -500,7 +543,9 @@ def test_skipping_setuptools_doesnt_skip_legacy(script, shared_data, tmpdir):
     result.did_not_create(wrapper_helper)
 
 
-def test_install_from_wheel_gui_entrypoint(script, shared_data, tmpdir):
+def test_install_from_wheel_gui_entrypoint(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing scripts (gui entry points are generated)
     """
@@ -519,7 +564,9 @@ def test_install_from_wheel_gui_entrypoint(script, shared_data, tmpdir):
     result.did_create(wrapper_file)
 
 
-def test_wheel_compiles_pyc(script, shared_data, tmpdir):
+def test_wheel_compiles_pyc(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing from wheel with --compile on
     """
@@ -536,16 +583,14 @@ def test_wheel_compiles_pyc(script, shared_data, tmpdir):
     #   any of them
     exists = [
         os.path.exists(script.site_packages_path / "simpledist/__init__.pyc"),
+        *glob.glob(script.site_packages_path / "simpledist/__pycache__/__init__*.pyc"),
     ]
-
-    exists += glob.glob(
-        script.site_packages_path / "simpledist/__pycache__/__init__*.pyc"
-    )
-
     assert any(exists)
 
 
-def test_wheel_no_compiles_pyc(script, shared_data, tmpdir):
+def test_wheel_no_compiles_pyc(
+    script: PipTestEnvironment, shared_data: TestData, tmpdir: Path
+) -> None:
     """
     Test installing from wheel with --compile on
     """
@@ -562,16 +607,15 @@ def test_wheel_no_compiles_pyc(script, shared_data, tmpdir):
     #   any of them
     exists = [
         os.path.exists(script.site_packages_path / "simpledist/__init__.pyc"),
+        *glob.glob(script.site_packages_path / "simpledist/__pycache__/__init__*.pyc"),
     ]
 
-    exists += glob.glob(
-        script.site_packages_path / "simpledist/__pycache__/__init__*.pyc"
-    )
-
     assert not any(exists)
 
 
-def test_install_from_wheel_uninstalls_old_version(script, data):
+def test_install_from_wheel_uninstalls_old_version(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     # regression test for https://github.com/pypa/pip/issues/1825
     package = data.packages.joinpath("simplewheel-1.0-py2.py3-none-any.whl")
     result = script.pip("install", package, "--no-index")
@@ -583,21 +627,23 @@ def test_install_from_wheel_uninstalls_old_version(script, data):
     result.did_not_create(dist_info_folder)
 
 
-def test_wheel_compile_syntax_error(script, data):
+def test_wheel_compile_syntax_error(script: PipTestEnvironment, data: TestData) -> None:
     package = data.packages.joinpath("compilewheel-1.0-py2.py3-none-any.whl")
     result = script.pip("install", "--compile", package, "--no-index")
     assert "yield from" not in result.stdout
     assert "SyntaxError: " not in result.stdout
 
 
-def test_wheel_install_with_no_cache_dir(script, data):
+def test_wheel_install_with_no_cache_dir(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Check wheel installations work, even with no cache."""
     package = data.packages.joinpath("simple.dist-0.1-py2.py3-none-any.whl")
     result = script.pip("install", "--no-cache-dir", "--no-index", package)
     result.assert_installed("simpledist", editable=False)
 
 
-def test_wheel_install_fails_with_extra_dist_info(script):
+def test_wheel_install_fails_with_extra_dist_info(script: PipTestEnvironment) -> None:
     package = create_basic_wheel_for_package(
         script,
         "simple",
@@ -613,7 +659,9 @@ def test_wheel_install_fails_with_extra_dist_info(script):
     assert "multiple .dist-info directories" in result.stderr
 
 
-def test_wheel_install_fails_with_unrelated_dist_info(script):
+def test_wheel_install_fails_with_unrelated_dist_info(
+    script: PipTestEnvironment,
+) -> None:
     package = create_basic_wheel_for_package(script, "simple", "0.1.0")
     new_name = "unrelated-2.0.0-py2.py3-none-any.whl"
     new_package = os.path.join(os.path.dirname(package), new_name)
@@ -630,7 +678,7 @@ def test_wheel_install_fails_with_unrelated_dist_info(script):
     assert "'simple-0.1.0.dist-info' does not start with 'unrelated'" in result.stderr
 
 
-def test_wheel_installs_ok_with_nested_dist_info(script):
+def test_wheel_installs_ok_with_nested_dist_info(script: PipTestEnvironment) -> None:
     package = create_basic_wheel_for_package(
         script,
         "simple",
@@ -645,7 +693,9 @@ def test_wheel_installs_ok_with_nested_dist_info(script):
     script.pip("install", "--no-cache-dir", "--no-index", package)
 
 
-def test_wheel_installs_ok_with_badly_encoded_irrelevant_dist_info_file(script):
+def test_wheel_installs_ok_with_badly_encoded_irrelevant_dist_info_file(
+    script: PipTestEnvironment,
+) -> None:
     package = create_basic_wheel_for_package(
         script,
         "simple",
@@ -655,7 +705,9 @@ def test_wheel_installs_ok_with_badly_encoded_irrelevant_dist_info_file(script):
     script.pip("install", "--no-cache-dir", "--no-index", package)
 
 
-def test_wheel_install_fails_with_badly_encoded_metadata(script):
+def test_wheel_install_fails_with_badly_encoded_metadata(
+    script: PipTestEnvironment,
+) -> None:
     package = create_basic_wheel_for_package(
         script,
         "simple",
@@ -674,7 +726,9 @@ def test_wheel_install_fails_with_badly_encoded_metadata(script):
     "package_name",
     ["simple-package", "simple_package"],
 )
-def test_correct_package_name_while_creating_wheel_bug(script, package_name):
+def test_correct_package_name_while_creating_wheel_bug(
+    script: PipTestEnvironment, package_name: str
+) -> None:
     """Check that the package name is correctly named while creating
     a .whl file with a given format
     """
@@ -684,7 +738,9 @@ def test_correct_package_name_while_creating_wheel_bug(script, package_name):
 
 
 @pytest.mark.parametrize("name", ["purelib", "abc"])
-def test_wheel_with_file_in_data_dir_has_reasonable_error(script, tmpdir, name):
+def test_wheel_with_file_in_data_dir_has_reasonable_error(
+    script: PipTestEnvironment, tmpdir: Path, name: str
+) -> None:
     """Normally we expect entities in the .data directory to be in a
     subdirectory, but if they are not then we should show a reasonable error
     message that includes the path.
@@ -697,7 +753,9 @@ def test_wheel_with_file_in_data_dir_has_reasonable_error(script, tmpdir, name):
     assert f"simple-0.1.0.data/{name}" in result.stderr
 
 
-def test_wheel_with_unknown_subdir_in_data_dir_has_reasonable_error(script, tmpdir):
+def test_wheel_with_unknown_subdir_in_data_dir_has_reasonable_error(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     wheel_path = make_wheel(
         "simple", "0.1.0", extra_data_files={"unknown/hello.txt": "hello world"}
     ).save_to_dir(tmpdir)
diff --git a/tests/functional/test_list.py b/tests/functional/test_list.py
index 80c72471d28..b9d0f0fa340 100644
--- a/tests/functional/test_list.py
+++ b/tests/functional/test_list.py
@@ -3,14 +3,25 @@
 
 import pytest
 
-from pip._internal.models.direct_url import DirectUrl
-from tests.lib import _create_test_package, create_test_package_with_setup, wheel
+from pip._internal.models.direct_url import DirectUrl, DirInfo
+from tests.conftest import ScriptFactory
+from tests.lib import (
+    PipTestEnvironment,
+    TestData,
+    _create_test_package,
+    create_test_package_with_setup,
+    wheel,
+)
 from tests.lib.direct_url import get_created_direct_url_path
 from tests.lib.path import Path
 
 
 @pytest.fixture(scope="session")
-def simple_script(tmpdir_factory, script_factory, shared_data):
+def simple_script(
+    tmpdir_factory: pytest.TempdirFactory,
+    script_factory: ScriptFactory,
+    shared_data: TestData,
+) -> PipTestEnvironment:
     tmpdir = Path(str(tmpdir_factory.mktemp("pip_test_package")))
     script = script_factory(tmpdir.joinpath("workspace"))
     script.pip(
@@ -24,7 +35,7 @@ def simple_script(tmpdir_factory, script_factory, shared_data):
     return script
 
 
-def test_basic_list(simple_script):
+def test_basic_list(simple_script: PipTestEnvironment) -> None:
     """
     Test default behavior of list command without format specifier.
 
@@ -34,7 +45,7 @@ def test_basic_list(simple_script):
     assert "simple2    3.0" in result.stdout, str(result)
 
 
-def test_verbose_flag(simple_script):
+def test_verbose_flag(simple_script: PipTestEnvironment) -> None:
     """
     Test the list command with the '-v' option
     """
@@ -47,7 +58,7 @@ def test_verbose_flag(simple_script):
     assert "simple2    3.0" in result.stdout, str(result)
 
 
-def test_columns_flag(simple_script):
+def test_columns_flag(simple_script: PipTestEnvironment) -> None:
     """
     Test the list command with the '--format=columns' option
     """
@@ -59,7 +70,7 @@ def test_columns_flag(simple_script):
     assert "simple2    3.0" in result.stdout, str(result)
 
 
-def test_format_priority(simple_script):
+def test_format_priority(simple_script: PipTestEnvironment) -> None:
     """
     Test that latest format has priority over previous ones.
     """
@@ -80,7 +91,7 @@ def test_format_priority(simple_script):
     assert "simple2    3.0" in result.stdout, str(result)
 
 
-def test_local_flag(simple_script):
+def test_local_flag(simple_script: PipTestEnvironment) -> None:
     """
     Test the behavior of --local flag in the list command
 
@@ -89,7 +100,7 @@ def test_local_flag(simple_script):
     assert {"name": "simple", "version": "1.0"} in json.loads(result.stdout)
 
 
-def test_local_columns_flag(simple_script):
+def test_local_columns_flag(simple_script: PipTestEnvironment) -> None:
     """
     Test the behavior of --local --format=columns flags in the list command
 
@@ -101,7 +112,9 @@ def test_local_columns_flag(simple_script):
     assert "simple     1.0" in result.stdout, str(result)
 
 
-def test_multiple_exclude_and_normalization(script, tmpdir):
+def test_multiple_exclude_and_normalization(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     req_path = wheel.make_wheel(name="Normalizable_Name", version="1.0").save_to_dir(
         tmpdir
     )
@@ -117,7 +130,7 @@ def test_multiple_exclude_and_normalization(script, tmpdir):
 
 @pytest.mark.network
 @pytest.mark.incompatible_with_test_venv
-def test_user_flag(script, data):
+def test_user_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test the behavior of --user flag in the list command
 
@@ -132,7 +145,7 @@ def test_user_flag(script, data):
 
 @pytest.mark.network
 @pytest.mark.incompatible_with_test_venv
-def test_user_columns_flag(script, data):
+def test_user_columns_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test the behavior of --user --format=columns flags in the list command
 
@@ -148,7 +161,7 @@ def test_user_columns_flag(script, data):
 
 
 @pytest.mark.network
-def test_uptodate_flag(script, data):
+def test_uptodate_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test the behavior of --uptodate flag in the list command
 
@@ -188,7 +201,7 @@ def test_uptodate_flag(script, data):
 
 
 @pytest.mark.network
-def test_uptodate_columns_flag(script, data):
+def test_uptodate_columns_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test the behavior of --uptodate --format=columns flag in the list command
 
@@ -223,7 +236,7 @@ def test_uptodate_columns_flag(script, data):
 
 
 @pytest.mark.network
-def test_outdated_flag(script, data):
+def test_outdated_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test the behavior of --outdated flag in the list command
 
@@ -283,7 +296,7 @@ def test_outdated_flag(script, data):
 
 
 @pytest.mark.network
-def test_outdated_columns_flag(script, data):
+def test_outdated_columns_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test the behavior of --outdated --format=columns flag in the list command
 
@@ -322,7 +335,11 @@ def test_outdated_columns_flag(script, data):
 
 
 @pytest.fixture(scope="session")
-def pip_test_package_script(tmpdir_factory, script_factory, shared_data):
+def pip_test_package_script(
+    tmpdir_factory: pytest.TempdirFactory,
+    script_factory: ScriptFactory,
+    shared_data: TestData,
+) -> PipTestEnvironment:
     tmpdir = Path(str(tmpdir_factory.mktemp("pip_test_package")))
     script = script_factory(tmpdir.joinpath("workspace"))
     script.pip("install", "-f", shared_data.find_links, "--no-index", "simple==1.0")
@@ -335,7 +352,7 @@ def pip_test_package_script(tmpdir_factory, script_factory, shared_data):
 
 
 @pytest.mark.network
-def test_editables_flag(pip_test_package_script):
+def test_editables_flag(pip_test_package_script: PipTestEnvironment) -> None:
     """
     Test the behavior of --editables flag in the list command
     """
@@ -346,7 +363,7 @@ def test_editables_flag(pip_test_package_script):
 
 
 @pytest.mark.network
-def test_exclude_editable_flag(pip_test_package_script):
+def test_exclude_editable_flag(pip_test_package_script: PipTestEnvironment) -> None:
     """
     Test the behavior of --editables flag in the list command
     """
@@ -356,7 +373,7 @@ def test_exclude_editable_flag(pip_test_package_script):
 
 
 @pytest.mark.network
-def test_editables_columns_flag(pip_test_package_script):
+def test_editables_columns_flag(pip_test_package_script: PipTestEnvironment) -> None:
     """
     Test the behavior of --editables flag in the list command
     """
@@ -368,7 +385,9 @@ def test_editables_columns_flag(pip_test_package_script):
 
 
 @pytest.mark.network
-def test_uptodate_editables_flag(pip_test_package_script, data):
+def test_uptodate_editables_flag(
+    pip_test_package_script: PipTestEnvironment, data: TestData
+) -> None:
     """
     test the behavior of --editable --uptodate flag in the list command
     """
@@ -385,7 +404,9 @@ def test_uptodate_editables_flag(pip_test_package_script, data):
 
 
 @pytest.mark.network
-def test_uptodate_editables_columns_flag(pip_test_package_script, data):
+def test_uptodate_editables_columns_flag(
+    pip_test_package_script: PipTestEnvironment, data: TestData
+) -> None:
     """
     test the behavior of --editable --uptodate --format=columns flag in the
     list command
@@ -406,7 +427,7 @@ def test_uptodate_editables_columns_flag(pip_test_package_script, data):
 
 
 @pytest.mark.network
-def test_outdated_editables_flag(script, data):
+def test_outdated_editables_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     test the behavior of --editable --outdated flag in the list command
     """
@@ -429,7 +450,9 @@ def test_outdated_editables_flag(script, data):
 
 
 @pytest.mark.network
-def test_outdated_editables_columns_flag(script, data):
+def test_outdated_editables_columns_flag(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     test the behavior of --editable --outdated flag in the list command
     """
@@ -454,7 +477,7 @@ def test_outdated_editables_columns_flag(script, data):
     assert os.path.join("src", "pip-test-package") in result.stdout, str(result)
 
 
-def test_outdated_not_required_flag(script, data):
+def test_outdated_not_required_flag(script: PipTestEnvironment, data: TestData) -> None:
     """
     test the behavior of --outdated --not-required flag in the list command
     """
@@ -478,7 +501,7 @@ def test_outdated_not_required_flag(script, data):
     assert [] == json.loads(result.stdout)
 
 
-def test_outdated_pre(script, data):
+def test_outdated_pre(script: PipTestEnvironment, data: TestData) -> None:
     script.pip("install", "-f", data.find_links, "--no-index", "simple==1.0")
 
     # Let's build a fake wheelhouse
@@ -525,7 +548,7 @@ def test_outdated_pre(script, data):
     } in json.loads(result_pre.stdout)
 
 
-def test_outdated_formats(script, data):
+def test_outdated_formats(script: PipTestEnvironment, data: TestData) -> None:
     """Test of different outdated formats"""
     script.pip("install", "-f", data.find_links, "--no-index", "simple==1.0")
 
@@ -585,7 +608,7 @@ def test_outdated_formats(script, data):
     ]
 
 
-def test_not_required_flag(script, data):
+def test_not_required_flag(script: PipTestEnvironment, data: TestData) -> None:
     script.pip("install", "-f", data.find_links, "--no-index", "TopoRequires4")
     result = script.pip("list", "--not-required", expect_stderr=True)
     assert "TopoRequires4 " in result.stdout, str(result)
@@ -594,7 +617,7 @@ def test_not_required_flag(script, data):
     assert "TopoRequires3 " not in result.stdout
 
 
-def test_list_freeze(simple_script):
+def test_list_freeze(simple_script: PipTestEnvironment) -> None:
     """
     Test freeze formatting of list command
 
@@ -604,7 +627,7 @@ def test_list_freeze(simple_script):
     assert "simple2==3.0" in result.stdout, str(result)
 
 
-def test_list_json(simple_script):
+def test_list_json(simple_script: PipTestEnvironment) -> None:
     """
     Test json formatting of list command
 
@@ -615,7 +638,7 @@ def test_list_json(simple_script):
     assert {"name": "simple2", "version": "3.0"} in data
 
 
-def test_list_path(tmpdir, script, data):
+def test_list_path(tmpdir: Path, script: PipTestEnvironment, data: TestData) -> None:
     """
     Test list with --path.
     """
@@ -630,7 +653,9 @@ def test_list_path(tmpdir, script, data):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_list_path_exclude_user(tmpdir, script, data):
+def test_list_path_exclude_user(
+    tmpdir: Path, script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test list with --path and make sure packages from --user are not picked
     up.
@@ -647,7 +672,9 @@ def test_list_path_exclude_user(tmpdir, script, data):
     assert {"name": "simple", "version": "1.0"} in json_result
 
 
-def test_list_path_multiple(tmpdir, script, data):
+def test_list_path_multiple(
+    tmpdir: Path, script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test list with multiple --path arguments.
     """
@@ -669,7 +696,7 @@ def test_list_path_multiple(tmpdir, script, data):
     assert {"name": "simple2", "version": "3.0"} in json_result
 
 
-def test_list_skip_work_dir_pkg(script):
+def test_list_skip_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that list should not include package in working directory
     """
@@ -684,7 +711,7 @@ def test_list_skip_work_dir_pkg(script):
     assert {"name": "simple", "version": "1.0"} not in json_result
 
 
-def test_list_include_work_dir_pkg(script):
+def test_list_include_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that list should include package in working directory
     if working directory is added in PYTHONPATH
@@ -703,7 +730,8 @@ def test_list_include_work_dir_pkg(script):
     assert {"name": "simple", "version": "1.0"} in json_result
 
 
-def test_list_pep610_editable(script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_list_pep610_editable(script: PipTestEnvironment) -> None:
     """
     Test that a package installed with a direct_url.json with editable=true
     is correctly listed as editable.
@@ -715,6 +743,7 @@ def test_list_pep610_editable(script, with_wheel):
     # patch direct_url.json to simulate an editable install
     with open(direct_url_path) as f:
         direct_url = DirectUrl.from_json(f.read())
+    assert isinstance(direct_url.info, DirInfo)
     direct_url.info.editable = True
     with open(direct_url_path, "w") as f:
         f.write(direct_url.to_json())
diff --git a/tests/functional/test_new_resolver.py b/tests/functional/test_new_resolver.py
index abff7d4f056..da36d41ccc7 100644
--- a/tests/functional/test_new_resolver.py
+++ b/tests/functional/test_new_resolver.py
@@ -2,10 +2,12 @@
 import pathlib
 import sys
 import textwrap
+from typing import TYPE_CHECKING, Callable, Dict, List, Tuple
 
 import pytest
 
 from tests.lib import (
+    PipTestEnvironment,
     create_basic_sdist_for_package,
     create_basic_wheel_for_package,
     create_test_package_with_setup,
@@ -15,8 +17,11 @@
 from tests.lib.path import Path
 from tests.lib.wheel import make_wheel
 
+if TYPE_CHECKING:
+    from typing import Protocol
 
-def assert_editable(script, *args):
+
+def assert_editable(script: PipTestEnvironment, *args: str) -> None:
     # This simply checks whether all of the listed packages have a
     # corresponding .egg-link file installed.
     # TODO: Implement a more rigorous way to test for editable installations.
@@ -27,8 +32,8 @@ def assert_editable(script, *args):
 
 
 @pytest.fixture()
-def make_fake_wheel(script):
-    def _make_fake_wheel(name, version, wheel_tag):
+def make_fake_wheel(script: PipTestEnvironment) -> Callable[[str, str, str], Path]:
+    def _make_fake_wheel(name: str, version: str, wheel_tag: str) -> Path:
         wheel_house = script.scratch_path.joinpath("wheelhouse")
         wheel_house.mkdir()
         wheel_builder = make_wheel(
@@ -43,7 +48,7 @@ def _make_fake_wheel(name, version, wheel_tag):
     return _make_fake_wheel
 
 
-def test_new_resolver_can_install(script):
+def test_new_resolver_can_install(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "simple",
@@ -60,7 +65,7 @@ def test_new_resolver_can_install(script):
     script.assert_installed(simple="0.1.0")
 
 
-def test_new_resolver_can_install_with_version(script):
+def test_new_resolver_can_install_with_version(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "simple",
@@ -77,7 +82,7 @@ def test_new_resolver_can_install_with_version(script):
     script.assert_installed(simple="0.1.0")
 
 
-def test_new_resolver_picks_latest_version(script):
+def test_new_resolver_picks_latest_version(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "simple",
@@ -99,7 +104,7 @@ def test_new_resolver_picks_latest_version(script):
     script.assert_installed(simple="0.2.0")
 
 
-def test_new_resolver_picks_installed_version(script):
+def test_new_resolver_picks_installed_version(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "simple",
@@ -132,7 +137,9 @@ def test_new_resolver_picks_installed_version(script):
     script.assert_installed(simple="0.1.0")
 
 
-def test_new_resolver_picks_installed_version_if_no_match_found(script):
+def test_new_resolver_picks_installed_version_if_no_match_found(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(
         script,
         "simple",
@@ -158,7 +165,7 @@ def test_new_resolver_picks_installed_version_if_no_match_found(script):
     script.assert_installed(simple="0.1.0")
 
 
-def test_new_resolver_installs_dependencies(script):
+def test_new_resolver_installs_dependencies(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -181,7 +188,7 @@ def test_new_resolver_installs_dependencies(script):
     script.assert_installed(base="0.1.0", dep="0.1.0")
 
 
-def test_new_resolver_ignore_dependencies(script):
+def test_new_resolver_ignore_dependencies(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -213,7 +220,9 @@ def test_new_resolver_ignore_dependencies(script):
         "base[add] >= 0.1.0",
     ],
 )
-def test_new_resolver_installs_extras(tmpdir, script, root_dep):
+def test_new_resolver_installs_extras(
+    tmpdir: Path, script: PipTestEnvironment, root_dep: str
+) -> None:
     req_file = tmpdir.joinpath("requirements.txt")
     req_file.write_text(root_dep)
 
@@ -240,7 +249,7 @@ def test_new_resolver_installs_extras(tmpdir, script, root_dep):
     script.assert_installed(base="0.1.0", dep="0.1.0")
 
 
-def test_new_resolver_installs_extras_warn_missing(script):
+def test_new_resolver_installs_extras_warn_missing(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -266,7 +275,7 @@ def test_new_resolver_installs_extras_warn_missing(script):
     script.assert_installed(base="0.1.0", dep="0.1.0")
 
 
-def test_new_resolver_installed_message(script):
+def test_new_resolver_installed_message(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "A", "1.0")
     result = script.pip(
         "install",
@@ -280,7 +289,7 @@ def test_new_resolver_installed_message(script):
     assert "Successfully installed A-1.0" in result.stdout, str(result)
 
 
-def test_new_resolver_no_dist_message(script):
+def test_new_resolver_no_dist_message(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "A", "1.0")
     result = script.pip(
         "install",
@@ -304,7 +313,7 @@ def test_new_resolver_no_dist_message(script):
     assert "No matching distribution found for B" in result.stderr, str(result)
 
 
-def test_new_resolver_installs_editable(script):
+def test_new_resolver_installs_editable(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -342,11 +351,11 @@ def test_new_resolver_installs_editable(script):
     ],
 )
 def test_new_resolver_requires_python(
-    script,
-    requires_python,
-    ignore_requires_python,
-    dep_version,
-):
+    script: PipTestEnvironment,
+    requires_python: str,
+    ignore_requires_python: bool,
+    dep_version: str,
+) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -381,7 +390,7 @@ def test_new_resolver_requires_python(
     script.assert_installed(base="0.1.0", dep=dep_version)
 
 
-def test_new_resolver_requires_python_error(script):
+def test_new_resolver_requires_python_error(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -405,7 +414,7 @@ def test_new_resolver_requires_python_error(script):
     assert message in result.stderr, str(result)
 
 
-def test_new_resolver_installed(script):
+def test_new_resolver_installed(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -442,7 +451,7 @@ def test_new_resolver_installed(script):
     )
 
 
-def test_new_resolver_ignore_installed(script):
+def test_new_resolver_ignore_installed(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -475,7 +484,9 @@ def test_new_resolver_ignore_installed(script):
     )
 
 
-def test_new_resolver_only_builds_sdists_when_needed(script):
+def test_new_resolver_only_builds_sdists_when_needed(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -518,7 +529,7 @@ def test_new_resolver_only_builds_sdists_when_needed(script):
     script.assert_installed(base="0.1.0", dep="0.2.0")
 
 
-def test_new_resolver_install_different_version(script):
+def test_new_resolver_install_different_version(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "base", "0.1.0")
     create_basic_wheel_for_package(script, "base", "0.2.0")
 
@@ -547,7 +558,7 @@ def test_new_resolver_install_different_version(script):
     script.assert_installed(base="0.2.0")
 
 
-def test_new_resolver_force_reinstall(script):
+def test_new_resolver_force_reinstall(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "base", "0.1.0")
 
     script.pip(
@@ -592,11 +603,11 @@ def test_new_resolver_force_reinstall(script):
     ids=["default", "exact-pre", "explicit-pre", "no-stable"],
 )
 def test_new_resolver_handles_prerelease(
-    script,
-    available_versions,
-    pip_args,
-    expected_version,
-):
+    script: PipTestEnvironment,
+    available_versions: List[str],
+    pip_args: List[str],
+    expected_version: str,
+) -> None:
     for version in available_versions:
         create_basic_wheel_for_package(script, "pkg", version)
     script.pip(
@@ -619,7 +630,9 @@ def test_new_resolver_handles_prerelease(
         ([], ["pkg", "dep; os_name == 'nonexist_os'"]),
     ],
 )
-def test_new_resolver_skips_marker(script, pkg_deps, root_deps):
+def test_new_resolver_skips_marker(
+    script: PipTestEnvironment, pkg_deps: List[str], root_deps: List[str]
+) -> None:
     create_basic_wheel_for_package(script, "pkg", "1.0", depends=pkg_deps)
     create_basic_wheel_for_package(script, "dep", "1.0")
 
@@ -644,7 +657,9 @@ def test_new_resolver_skips_marker(script, pkg_deps, root_deps):
         ["pkg<2.0"],
     ],
 )
-def test_new_resolver_constraints(script, constraints):
+def test_new_resolver_constraints(
+    script: PipTestEnvironment, constraints: List[str]
+) -> None:
     create_basic_wheel_for_package(script, "pkg", "1.0")
     create_basic_wheel_for_package(script, "pkg", "2.0")
     create_basic_wheel_for_package(script, "pkg", "3.0")
@@ -664,7 +679,7 @@ def test_new_resolver_constraints(script, constraints):
     script.assert_not_installed("constraint_only")
 
 
-def test_new_resolver_constraint_no_specifier(script):
+def test_new_resolver_constraint_no_specifier(script: PipTestEnvironment) -> None:
     "It's allowed (but useless...) for a constraint to have no specifier"
     create_basic_wheel_for_package(script, "pkg", "1.0")
     constraints_file = script.scratch_path / "constraints.txt"
@@ -699,7 +714,9 @@ def test_new_resolver_constraint_no_specifier(script):
         ),
     ],
 )
-def test_new_resolver_constraint_reject_invalid(script, constraint, error):
+def test_new_resolver_constraint_reject_invalid(
+    script: PipTestEnvironment, constraint: str, error: str
+) -> None:
     create_basic_wheel_for_package(script, "pkg", "1.0")
     constraints_file = script.scratch_path / "constraints.txt"
     constraints_file.write_text(constraint)
@@ -718,7 +735,7 @@ def test_new_resolver_constraint_reject_invalid(script, constraint, error):
     assert error in result.stderr, str(result)
 
 
-def test_new_resolver_constraint_on_dependency(script):
+def test_new_resolver_constraint_on_dependency(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "base", "1.0", depends=["dep"])
     create_basic_wheel_for_package(script, "dep", "1.0")
     create_basic_wheel_for_package(script, "dep", "2.0")
@@ -747,11 +764,11 @@ def test_new_resolver_constraint_on_dependency(script):
     ],
 )
 def test_new_resolver_constraint_on_path_empty(
-    script,
-    constraint_version,
-    expect_error,
-    message,
-):
+    script: PipTestEnvironment,
+    constraint_version: str,
+    expect_error: bool,
+    message: str,
+) -> None:
     """A path requirement can be filtered by a constraint."""
     setup_py = script.scratch_path / "setup.py"
     text = "from setuptools import setup\nsetup(name='foo', version='2.0')"
@@ -776,7 +793,7 @@ def test_new_resolver_constraint_on_path_empty(
         assert message in result.stdout, str(result)
 
 
-def test_new_resolver_constraint_only_marker_match(script):
+def test_new_resolver_constraint_only_marker_match(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "pkg", "1.0")
     create_basic_wheel_for_package(script, "pkg", "2.0")
     create_basic_wheel_for_package(script, "pkg", "3.0")
@@ -803,7 +820,7 @@ def test_new_resolver_constraint_only_marker_match(script):
     script.assert_installed(pkg="1.0")
 
 
-def test_new_resolver_upgrade_needs_option(script):
+def test_new_resolver_upgrade_needs_option(script: PipTestEnvironment) -> None:
     # Install pkg 1.0.0
     create_basic_wheel_for_package(script, "pkg", "1.0.0")
     script.pip(
@@ -848,7 +865,7 @@ def test_new_resolver_upgrade_needs_option(script):
     script.assert_installed(pkg="2.0.0")
 
 
-def test_new_resolver_upgrade_strategy(script):
+def test_new_resolver_upgrade_strategy(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "base", "1.0.0", depends=["dep"])
     create_basic_wheel_for_package(script, "dep", "1.0.0")
     script.pip(
@@ -899,43 +916,78 @@ def test_new_resolver_upgrade_strategy(script):
     script.assert_installed(dep="2.0.0")
 
 
+if TYPE_CHECKING:
+
+    class PackageBuilder(Protocol):
+        def __call__(
+            self,
+            script: PipTestEnvironment,
+            name: str,
+            version: str,
+            requires: List[str],
+            extras: Dict[str, List[str]],
+        ) -> str:
+            ...
+
+
+def _local_with_setup(
+    script: PipTestEnvironment,
+    name: str,
+    version: str,
+    requires: List[str],
+    extras: Dict[str, List[str]],
+) -> str:
+    """Create the package as a local source directory to install from path."""
+    return create_test_package_with_setup(
+        script,
+        name=name,
+        version=version,
+        install_requires=requires,
+        extras_require=extras,
+    )
+
+
+def _direct_wheel(
+    script: PipTestEnvironment,
+    name: str,
+    version: str,
+    requires: List[str],
+    extras: Dict[str, List[str]],
+) -> str:
+    """Create the package as a wheel to install from path directly."""
+    return create_basic_wheel_for_package(
+        script,
+        name=name,
+        version=version,
+        depends=requires,
+        extras=extras,
+    )
+
+
+def _wheel_from_index(
+    script: PipTestEnvironment,
+    name: str,
+    version: str,
+    requires: List[str],
+    extras: Dict[str, List[str]],
+) -> str:
+    """Create the package as a wheel to install from index."""
+    create_basic_wheel_for_package(
+        script,
+        name=name,
+        version=version,
+        depends=requires,
+        extras=extras,
+    )
+    return name
+
+
 class TestExtraMerge:
     """
     Test installing a package that depends the same package with different
     extras, one listed as required and the other as in extra.
     """
 
-    def _local_with_setup(script, name, version, requires, extras):
-        """Create the package as a local source directory to install from path."""
-        return create_test_package_with_setup(
-            script,
-            name=name,
-            version=version,
-            install_requires=requires,
-            extras_require=extras,
-        )
-
-    def _direct_wheel(script, name, version, requires, extras):
-        """Create the package as a wheel to install from path directly."""
-        return create_basic_wheel_for_package(
-            script,
-            name=name,
-            version=version,
-            depends=requires,
-            extras=extras,
-        )
-
-    def _wheel_from_index(script, name, version, requires, extras):
-        """Create the package as a wheel to install from index."""
-        create_basic_wheel_for_package(
-            script,
-            name=name,
-            version=version,
-            depends=requires,
-            extras=extras,
-        )
-        return name
-
     @pytest.mark.parametrize(
         "pkg_builder",
         [
@@ -944,7 +996,9 @@ def _wheel_from_index(script, name, version, requires, extras):
             _wheel_from_index,
         ],
     )
-    def test_new_resolver_extra_merge_in_package(self, script, pkg_builder):
+    def test_new_resolver_extra_merge_in_package(
+        self, script: PipTestEnvironment, pkg_builder: "PackageBuilder"
+    ) -> None:
         create_basic_wheel_for_package(script, "depdev", "1.0.0")
         create_basic_wheel_for_package(
             script,
@@ -971,7 +1025,7 @@ def test_new_resolver_extra_merge_in_package(self, script, pkg_builder):
         script.assert_installed(pkg="1.0.0", dep="1.0.0", depdev="1.0.0")
 
 
-def test_new_resolver_build_directory_error_zazo_19(script):
+def test_new_resolver_build_directory_error_zazo_19(script: PipTestEnvironment) -> None:
     """https://github.com/pradyunsg/zazo/issues/19#issuecomment-631615674
 
     This will first resolve like this:
@@ -1016,7 +1070,7 @@ def test_new_resolver_build_directory_error_zazo_19(script):
     script.assert_installed(pkg_a="3.0.0", pkg_b="1.0.0")
 
 
-def test_new_resolver_upgrade_same_version(script):
+def test_new_resolver_upgrade_same_version(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "pkg", "2")
     create_basic_wheel_for_package(script, "pkg", "1")
 
@@ -1042,7 +1096,7 @@ def test_new_resolver_upgrade_same_version(script):
     script.assert_installed(pkg="2")
 
 
-def test_new_resolver_local_and_req(script):
+def test_new_resolver_local_and_req(script: PipTestEnvironment) -> None:
     source_dir = create_test_package_with_setup(
         script,
         name="pkg",
@@ -1058,7 +1112,9 @@ def test_new_resolver_local_and_req(script):
     )
 
 
-def test_new_resolver_no_deps_checks_requires_python(script):
+def test_new_resolver_no_deps_checks_requires_python(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(
         script,
         "base",
@@ -1090,7 +1146,9 @@ def test_new_resolver_no_deps_checks_requires_python(script):
     assert message in result.stderr
 
 
-def test_new_resolver_prefers_installed_in_upgrade_if_latest(script):
+def test_new_resolver_prefers_installed_in_upgrade_if_latest(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(script, "pkg", "1")
     local_pkg = create_test_package_with_setup(script, name="pkg", version="2")
 
@@ -1116,7 +1174,9 @@ def test_new_resolver_prefers_installed_in_upgrade_if_latest(script):
 
 
 @pytest.mark.parametrize("N", [2, 10, 20])
-def test_new_resolver_presents_messages_when_backtracking_a_lot(script, N):
+def test_new_resolver_presents_messages_when_backtracking_a_lot(
+    script: PipTestEnvironment, N: int
+) -> None:
     # Generate a set of wheels that will definitely cause backtracking.
     for index in range(1, N + 1):
         A_version = f"{index}.0.0"
@@ -1186,10 +1246,10 @@ def test_new_resolver_presents_messages_when_backtracking_a_lot(script, N):
     ids=["file_dot", "file_underscore"],
 )
 def test_new_resolver_check_wheel_version_normalized(
-    script,
-    metadata_version,
-    filename_version,
-):
+    script: PipTestEnvironment,
+    metadata_version: str,
+    filename_version: str,
+) -> None:
     filename = f"simple-{filename_version}-py2.py3-none-any.whl"
 
     wheel_builder = make_wheel(name="simple", version=metadata_version)
@@ -1206,7 +1266,7 @@ def test_new_resolver_check_wheel_version_normalized(
     script.assert_installed(simple="0.1.0+local.1")
 
 
-def test_new_resolver_does_reinstall_local_sdists(script):
+def test_new_resolver_does_reinstall_local_sdists(script: PipTestEnvironment) -> None:
     archive_path = create_basic_sdist_for_package(
         script,
         "pkg",
@@ -1231,7 +1291,7 @@ def test_new_resolver_does_reinstall_local_sdists(script):
     script.assert_installed(pkg="1.0")
 
 
-def test_new_resolver_does_reinstall_local_paths(script):
+def test_new_resolver_does_reinstall_local_paths(script: PipTestEnvironment) -> None:
     pkg = create_test_package_with_setup(script, name="pkg", version="1.0")
     script.pip(
         "install",
@@ -1251,7 +1311,9 @@ def test_new_resolver_does_reinstall_local_paths(script):
     script.assert_installed(pkg="1.0")
 
 
-def test_new_resolver_does_not_reinstall_when_from_a_local_index(script):
+def test_new_resolver_does_not_reinstall_when_from_a_local_index(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_sdist_for_package(
         script,
         "simple",
@@ -1281,7 +1343,7 @@ def test_new_resolver_does_not_reinstall_when_from_a_local_index(script):
     script.assert_installed(simple="0.1.0")
 
 
-def test_new_resolver_skip_inconsistent_metadata(script):
+def test_new_resolver_skip_inconsistent_metadata(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "A", "1")
 
     a_2 = create_basic_wheel_for_package(script, "A", "2")
@@ -1309,7 +1371,9 @@ def test_new_resolver_skip_inconsistent_metadata(script):
     [True, False],
     ids=["upgrade", "no-upgrade"],
 )
-def test_new_resolver_lazy_fetch_candidates(script, upgrade):
+def test_new_resolver_lazy_fetch_candidates(
+    script: PipTestEnvironment, upgrade: bool
+) -> None:
     create_basic_wheel_for_package(script, "myuberpkg", "1")
     create_basic_wheel_for_package(script, "myuberpkg", "2")
     create_basic_wheel_for_package(script, "myuberpkg", "3")
@@ -1350,7 +1414,7 @@ def test_new_resolver_lazy_fetch_candidates(script, upgrade):
     assert "myuberpkg-2" not in result.stdout, str(result)
 
 
-def test_new_resolver_no_fetch_no_satisfying(script):
+def test_new_resolver_no_fetch_no_satisfying(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "myuberpkg", "1")
 
     # Install the package. This should emit a "Processing" message for
@@ -1379,7 +1443,9 @@ def test_new_resolver_no_fetch_no_satisfying(script):
     assert "Processing " not in result.stdout, str(result)
 
 
-def test_new_resolver_does_not_install_unneeded_packages_with_url_constraint(script):
+def test_new_resolver_does_not_install_unneeded_packages_with_url_constraint(
+    script: PipTestEnvironment,
+) -> None:
     archive_path = create_basic_wheel_for_package(
         script,
         "installed",
@@ -1412,7 +1478,9 @@ def test_new_resolver_does_not_install_unneeded_packages_with_url_constraint(scr
     script.assert_not_installed("not_installed")
 
 
-def test_new_resolver_installs_packages_with_url_constraint(script):
+def test_new_resolver_installs_packages_with_url_constraint(
+    script: PipTestEnvironment,
+) -> None:
     installed_path = create_basic_wheel_for_package(
         script,
         "installed",
@@ -1429,7 +1497,9 @@ def test_new_resolver_installs_packages_with_url_constraint(script):
     script.assert_installed(installed="0.1.0")
 
 
-def test_new_resolver_reinstall_link_requirement_with_constraint(script):
+def test_new_resolver_reinstall_link_requirement_with_constraint(
+    script: PipTestEnvironment,
+) -> None:
     installed_path = create_basic_wheel_for_package(
         script,
         "installed",
@@ -1462,7 +1532,7 @@ def test_new_resolver_reinstall_link_requirement_with_constraint(script):
     script.assert_installed(installed="0.1.0")
 
 
-def test_new_resolver_prefers_url_constraint(script):
+def test_new_resolver_prefers_url_constraint(script: PipTestEnvironment) -> None:
     installed_path = create_basic_wheel_for_package(
         script,
         "test_pkg",
@@ -1494,7 +1564,9 @@ def test_new_resolver_prefers_url_constraint(script):
     script.assert_installed(test_pkg="0.1.0")
 
 
-def test_new_resolver_prefers_url_constraint_on_update(script):
+def test_new_resolver_prefers_url_constraint_on_update(
+    script: PipTestEnvironment,
+) -> None:
     installed_path = create_basic_wheel_for_package(
         script,
         "test_pkg",
@@ -1539,9 +1611,9 @@ def test_new_resolver_prefers_url_constraint_on_update(script):
 
 @pytest.mark.parametrize("version_option", ["--constraint", "--requirement"])
 def test_new_resolver_fails_with_url_constraint_and_incompatible_version(
-    script,
-    version_option,
-):
+    script: PipTestEnvironment,
+    version_option: str,
+) -> None:
     not_installed_path = create_basic_wheel_for_package(
         script,
         "test_pkg",
@@ -1593,7 +1665,9 @@ def test_new_resolver_fails_with_url_constraint_and_incompatible_version(
     )
 
 
-def test_new_resolver_ignores_unneeded_conflicting_constraints(script):
+def test_new_resolver_ignores_unneeded_conflicting_constraints(
+    script: PipTestEnvironment,
+) -> None:
     version_1 = create_basic_wheel_for_package(
         script,
         "test_pkg",
@@ -1633,7 +1707,9 @@ def test_new_resolver_ignores_unneeded_conflicting_constraints(script):
     script.assert_installed(installed="0.1.0")
 
 
-def test_new_resolver_fails_on_needed_conflicting_constraints(script):
+def test_new_resolver_fails_on_needed_conflicting_constraints(
+    script: PipTestEnvironment,
+) -> None:
     version_1 = create_basic_wheel_for_package(
         script,
         "test_pkg",
@@ -1683,7 +1759,9 @@ def test_new_resolver_fails_on_needed_conflicting_constraints(script):
     )
 
 
-def test_new_resolver_fails_on_conflicting_constraint_and_requirement(script):
+def test_new_resolver_fails_on_conflicting_constraint_and_requirement(
+    script: PipTestEnvironment,
+) -> None:
     version_1 = create_basic_wheel_for_package(
         script,
         "test_pkg",
@@ -1729,7 +1807,9 @@ def test_new_resolver_fails_on_conflicting_constraint_and_requirement(script):
 
 
 @pytest.mark.parametrize("editable", [False, True])
-def test_new_resolver_succeeds_on_matching_constraint_and_requirement(script, editable):
+def test_new_resolver_succeeds_on_matching_constraint_and_requirement(
+    script: PipTestEnvironment, editable: bool
+) -> None:
     if editable:
         source_dir = create_test_package_with_setup(
             script, name="test_pkg", version="0.1.0"
@@ -1746,6 +1826,7 @@ def test_new_resolver_succeeds_on_matching_constraint_and_requirement(script, ed
     constraints_file = script.scratch_path / "constraints.txt"
     constraints_file.write_text(req_line)
 
+    last_args: Tuple[str, ...]
     if editable:
         last_args = ("-e", source_dir)
     else:
@@ -1765,7 +1846,7 @@ def test_new_resolver_succeeds_on_matching_constraint_and_requirement(script, ed
         assert_editable(script, "test-pkg")
 
 
-def test_new_resolver_applies_url_constraint_to_dep(script):
+def test_new_resolver_applies_url_constraint_to_dep(script: PipTestEnvironment) -> None:
     version_1 = create_basic_wheel_for_package(
         script,
         "dep",
@@ -1801,8 +1882,8 @@ def test_new_resolver_applies_url_constraint_to_dep(script):
 
 
 def test_new_resolver_handles_compatible_wheel_tags_in_constraint_url(
-    script, make_fake_wheel
-):
+    script: PipTestEnvironment, make_fake_wheel: Callable[[str, str, str], Path]
+) -> None:
     initial_path = make_fake_wheel("base", "0.1.0", "fakepy1-fakeabi-fakeplat")
 
     constrained = script.scratch_path / "constrained"
@@ -1840,8 +1921,8 @@ def test_new_resolver_handles_compatible_wheel_tags_in_constraint_url(
 
 
 def test_new_resolver_handles_incompatible_wheel_tags_in_constraint_url(
-    script, make_fake_wheel
-):
+    script: PipTestEnvironment, make_fake_wheel: Callable[[str, str, str], Path]
+) -> None:
     initial_path = make_fake_wheel("base", "0.1.0", "fakepy1-fakeabi-fakeplat")
 
     constrained = script.scratch_path / "constrained"
@@ -1873,8 +1954,8 @@ def test_new_resolver_handles_incompatible_wheel_tags_in_constraint_url(
 
 
 def test_new_resolver_avoids_incompatible_wheel_tags_in_constraint_url(
-    script, make_fake_wheel
-):
+    script: PipTestEnvironment, make_fake_wheel: Callable[[str, str, str], Path]
+) -> None:
     initial_path = make_fake_wheel("dep", "0.1.0", "fakepy1-fakeabi-fakeplat")
 
     constrained = script.scratch_path / "constrained"
@@ -1968,12 +2049,12 @@ def test_new_resolver_avoids_incompatible_wheel_tags_in_constraint_url(
     ],
 )
 def test_new_resolver_direct_url_equivalent(
-    tmp_path,
-    script,
-    suffixes_equivalent,
-    depend_suffix,
-    request_suffix,
-):
+    tmp_path: pathlib.Path,
+    script: PipTestEnvironment,
+    suffixes_equivalent: bool,
+    depend_suffix: str,
+    request_suffix: str,
+) -> None:
     pkga = create_basic_wheel_for_package(script, name="pkga", version="1")
     pkgb = create_basic_wheel_for_package(
         script,
@@ -2007,7 +2088,9 @@ def test_new_resolver_direct_url_equivalent(
         script.assert_not_installed("pkga", "pkgb")
 
 
-def test_new_resolver_direct_url_with_extras(tmp_path, script):
+def test_new_resolver_direct_url_with_extras(
+    tmp_path: pathlib.Path, script: PipTestEnvironment
+) -> None:
     pkg1 = create_basic_wheel_for_package(script, name="pkg1", version="1")
     pkg2 = create_basic_wheel_for_package(
         script,
@@ -2048,7 +2131,9 @@ def test_new_resolver_direct_url_with_extras(tmp_path, script):
     assert not get_created_direct_url(result, "pkg3")
 
 
-def test_new_resolver_modifies_installed_incompatible(script):
+def test_new_resolver_modifies_installed_incompatible(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(script, name="a", version="1")
     create_basic_wheel_for_package(script, name="a", version="2")
     create_basic_wheel_for_package(script, name="a", version="3")
@@ -2082,7 +2167,9 @@ def test_new_resolver_modifies_installed_incompatible(script):
     script.assert_installed(d="1", c="2", b="2", a="2")
 
 
-def test_new_resolver_transitively_depends_on_unnamed_local(script):
+def test_new_resolver_transitively_depends_on_unnamed_local(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(script, name="certbot-docs", version="1")
     certbot = create_test_package_with_setup(
         script,
@@ -2113,12 +2200,12 @@ def test_new_resolver_transitively_depends_on_unnamed_local(script):
     )
 
 
-def _to_uri(path):
+def _to_uri(path: str) -> str:
     # Something like file:///path/to/package
     return pathlib.Path(path).as_uri()
 
 
-def _to_localhost_uri(path):
+def _to_localhost_uri(path: str) -> str:
     # Something like file://localhost/path/to/package
     return pathlib.Path(path).as_uri().replace("///", "//localhost/")
 
@@ -2138,7 +2225,11 @@ def _to_localhost_uri(path):
         pytest.param(_to_localhost_uri, id="localhost"),
     ],
 )
-def test_new_resolver_file_url_normalize(script, format_dep, format_input):
+def test_new_resolver_file_url_normalize(
+    script: PipTestEnvironment,
+    format_dep: Callable[[str], str],
+    format_input: Callable[[str], str],
+) -> None:
     lib_a = create_test_package_with_setup(
         script,
         name="lib_a",
@@ -2161,7 +2252,9 @@ def test_new_resolver_file_url_normalize(script, format_dep, format_input):
     script.assert_installed(lib_a="1", lib_b="1")
 
 
-def test_new_resolver_dont_backtrack_on_extra_if_base_constrained(script):
+def test_new_resolver_dont_backtrack_on_extra_if_base_constrained(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(script, "dep", "1.0")
     create_basic_wheel_for_package(script, "pkg", "1.0", extras={"ext": ["dep"]})
     create_basic_wheel_for_package(script, "pkg", "2.0", extras={"ext": ["dep"]})
@@ -2182,7 +2275,9 @@ def test_new_resolver_dont_backtrack_on_extra_if_base_constrained(script):
     script.assert_installed(pkg="1.0", dep="1.0")
 
 
-def test_new_resolver_respect_user_requested_if_extra_is_installed(script):
+def test_new_resolver_respect_user_requested_if_extra_is_installed(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(script, "pkg1", "1.0")
     create_basic_wheel_for_package(script, "pkg2", "1.0", extras={"ext": ["pkg1"]})
     create_basic_wheel_for_package(script, "pkg2", "2.0", extras={"ext": ["pkg1"]})
diff --git a/tests/functional/test_new_resolver_errors.py b/tests/functional/test_new_resolver_errors.py
index b744a2b159e..1278bc3edde 100644
--- a/tests/functional/test_new_resolver_errors.py
+++ b/tests/functional/test_new_resolver_errors.py
@@ -1,10 +1,17 @@
 import pathlib
 import sys
 
-from tests.lib import create_basic_wheel_for_package, create_test_package_with_setup
+from tests.lib import (
+    PipTestEnvironment,
+    create_basic_wheel_for_package,
+    create_test_package_with_setup,
+)
+from tests.lib.path import Path
 
 
-def test_new_resolver_conflict_requirements_file(tmpdir, script):
+def test_new_resolver_conflict_requirements_file(
+    tmpdir: Path, script: PipTestEnvironment
+) -> None:
     create_basic_wheel_for_package(script, "base", "1.0")
     create_basic_wheel_for_package(script, "base", "2.0")
     create_basic_wheel_for_package(
@@ -38,7 +45,9 @@ def test_new_resolver_conflict_requirements_file(tmpdir, script):
     assert message in result.stderr, str(result)
 
 
-def test_new_resolver_conflict_constraints_file(tmpdir, script):
+def test_new_resolver_conflict_constraints_file(
+    tmpdir: Path, script: PipTestEnvironment
+) -> None:
     create_basic_wheel_for_package(script, "pkg", "1.0")
 
     constraints_file = tmpdir.joinpath("constraints.txt")
@@ -62,7 +71,7 @@ def test_new_resolver_conflict_constraints_file(tmpdir, script):
     assert message in result.stdout, str(result)
 
 
-def test_new_resolver_requires_python_error(script):
+def test_new_resolver_requires_python_error(script: PipTestEnvironment) -> None:
     compatible_python = ">={0.major}.{0.minor}".format(sys.version_info)
     incompatible_python = "<{0.major}.{0.minor}".format(sys.version_info)
 
@@ -88,7 +97,9 @@ def test_new_resolver_requires_python_error(script):
     assert compatible_python not in result.stderr, str(result)
 
 
-def test_new_resolver_checks_requires_python_before_dependencies(script):
+def test_new_resolver_checks_requires_python_before_dependencies(
+    script: PipTestEnvironment,
+) -> None:
     incompatible_python = "<{0.major}.{0.minor}".format(sys.version_info)
 
     pkg_dep = create_basic_wheel_for_package(
diff --git a/tests/functional/test_new_resolver_hashes.py b/tests/functional/test_new_resolver_hashes.py
index bf7e75109ca..b3812011254 100644
--- a/tests/functional/test_new_resolver_hashes.py
+++ b/tests/functional/test_new_resolver_hashes.py
@@ -4,7 +4,11 @@
 import pytest
 
 from pip._internal.utils.urls import path_to_url
-from tests.lib import create_basic_sdist_for_package, create_basic_wheel_for_package
+from tests.lib import (
+    PipTestEnvironment,
+    create_basic_sdist_for_package,
+    create_basic_wheel_for_package,
+)
 
 _FindLinks = collections.namedtuple(
     "_FindLinks",
@@ -12,7 +16,7 @@
 )
 
 
-def _create_find_links(script):
+def _create_find_links(script: PipTestEnvironment) -> _FindLinks:
     sdist_path = create_basic_sdist_for_package(script, "base", "0.1.0")
     wheel_path = create_basic_wheel_for_package(script, "base", "0.1.0")
 
@@ -60,7 +64,9 @@ def _create_find_links(script):
     ],
     ids=["identical", "intersect"],
 )
-def test_new_resolver_hash_intersect(script, requirements_template, message):
+def test_new_resolver_hash_intersect(
+    script: PipTestEnvironment, requirements_template: str, message: str
+) -> None:
     find_links = _create_find_links(script)
 
     requirements_txt = script.scratch_path / "requirements.txt"
@@ -86,7 +92,9 @@ def test_new_resolver_hash_intersect(script, requirements_template, message):
     assert message.format(name="base") in result.stdout, str(result)
 
 
-def test_new_resolver_hash_intersect_from_constraint(script):
+def test_new_resolver_hash_intersect_from_constraint(
+    script: PipTestEnvironment,
+) -> None:
     find_links = _create_find_links(script)
 
     constraints_txt = script.scratch_path / "constraints.txt"
@@ -144,10 +152,10 @@ def test_new_resolver_hash_intersect_from_constraint(script):
     ids=["both-requirements", "one-each"],
 )
 def test_new_resolver_hash_intersect_empty(
-    script,
-    requirements_template,
-    constraints_template,
-):
+    script: PipTestEnvironment,
+    requirements_template: str,
+    constraints_template: str,
+) -> None:
     find_links = _create_find_links(script)
 
     constraints_txt = script.scratch_path / "constraints.txt"
@@ -185,7 +193,9 @@ def test_new_resolver_hash_intersect_empty(
     ) in result.stderr, str(result)
 
 
-def test_new_resolver_hash_intersect_empty_from_constraint(script):
+def test_new_resolver_hash_intersect_empty_from_constraint(
+    script: PipTestEnvironment,
+) -> None:
     find_links = _create_find_links(script)
 
     constraints_txt = script.scratch_path / "constraints.txt"
@@ -221,9 +231,9 @@ def test_new_resolver_hash_intersect_empty_from_constraint(script):
 
 @pytest.mark.parametrize("constrain_by_hash", [False, True])
 def test_new_resolver_hash_requirement_and_url_constraint_can_succeed(
-    script,
-    constrain_by_hash,
-):
+    script: PipTestEnvironment,
+    constrain_by_hash: bool,
+) -> None:
     wheel_path = create_basic_wheel_for_package(script, "base", "0.1.0")
 
     wheel_hash = hashlib.sha256(wheel_path.read_bytes()).hexdigest()
@@ -260,9 +270,9 @@ def test_new_resolver_hash_requirement_and_url_constraint_can_succeed(
 
 @pytest.mark.parametrize("constrain_by_hash", [False, True])
 def test_new_resolver_hash_requirement_and_url_constraint_can_fail(
-    script,
-    constrain_by_hash,
-):
+    script: PipTestEnvironment,
+    constrain_by_hash: bool,
+) -> None:
     wheel_path = create_basic_wheel_for_package(script, "base", "0.1.0")
     other_path = create_basic_wheel_for_package(script, "other", "0.1.0")
 
diff --git a/tests/functional/test_new_resolver_target.py b/tests/functional/test_new_resolver_target.py
index 1f29f4a1121..398695b5a83 100644
--- a/tests/functional/test_new_resolver_target.py
+++ b/tests/functional/test_new_resolver_target.py
@@ -1,13 +1,18 @@
+from typing import Callable, Optional
+
 import pytest
 
 from pip._internal.cli.status_codes import ERROR, SUCCESS
+from tests.lib import PipTestEnvironment
 from tests.lib.path import Path
 from tests.lib.wheel import make_wheel
 
+MakeFakeWheel = Callable[[str], Path]
+
 
 @pytest.fixture()
-def make_fake_wheel(script):
-    def _make_fake_wheel(wheel_tag):
+def make_fake_wheel(script: PipTestEnvironment) -> MakeFakeWheel:
+    def _make_fake_wheel(wheel_tag: str) -> Path:
         wheel_house = script.scratch_path.joinpath("wheelhouse")
         wheel_house.mkdir()
         wheel_builder = make_wheel(
@@ -27,13 +32,13 @@ def _make_fake_wheel(wheel_tag):
 @pytest.mark.parametrize("abi", [None, "fakeabi"])
 @pytest.mark.parametrize("platform", [None, "fakeplat"])
 def test_new_resolver_target_checks_compatibility_failure(
-    script,
-    make_fake_wheel,
-    implementation,
-    python_version,
-    abi,
-    platform,
-):
+    script: PipTestEnvironment,
+    make_fake_wheel: MakeFakeWheel,
+    implementation: Optional[str],
+    python_version: Optional[str],
+    abi: Optional[str],
+    platform: Optional[str],
+) -> None:
     fake_wheel_tag = "fakepy1-fakeabi-fakeplat"
     args = [
         "install",
diff --git a/tests/functional/test_new_resolver_user.py b/tests/functional/test_new_resolver_user.py
index f98250c785b..e664ee33927 100644
--- a/tests/functional/test_new_resolver_user.py
+++ b/tests/functional/test_new_resolver_user.py
@@ -3,11 +3,12 @@
 
 import pytest
 
-from tests.lib import create_basic_wheel_for_package
+from tests.lib import PipTestEnvironment, create_basic_wheel_for_package
+from tests.lib.venv import VirtualEnvironment
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_new_resolver_install_user(script):
+def test_new_resolver_install_user(script: PipTestEnvironment) -> None:
     create_basic_wheel_for_package(script, "base", "0.1.0")
     result = script.pip(
         "install",
@@ -22,7 +23,9 @@ def test_new_resolver_install_user(script):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_new_resolver_install_user_satisfied_by_global_site(script):
+def test_new_resolver_install_user_satisfied_by_global_site(
+    script: PipTestEnvironment,
+) -> None:
     """
     An install a matching version to user site should re-use a global site
     installation if it satisfies.
@@ -51,7 +54,9 @@ def test_new_resolver_install_user_satisfied_by_global_site(script):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_new_resolver_install_user_conflict_in_user_site(script):
+def test_new_resolver_install_user_conflict_in_user_site(
+    script: PipTestEnvironment,
+) -> None:
     """
     Installing a different version in user site should uninstall an existing
     different version in user site.
@@ -87,7 +92,9 @@ def test_new_resolver_install_user_conflict_in_user_site(script):
 
 
 @pytest.mark.incompatible_with_test_venv
-def test_new_resolver_install_user_in_virtualenv_with_conflict_fails(script):
+def test_new_resolver_install_user_in_virtualenv_with_conflict_fails(
+    script: PipTestEnvironment,
+) -> None:
     create_basic_wheel_for_package(script, "base", "1.0.0")
     create_basic_wheel_for_package(script, "base", "2.0.0")
 
@@ -118,7 +125,7 @@ def test_new_resolver_install_user_in_virtualenv_with_conflict_fails(script):
 
 
 @pytest.fixture()
-def patch_dist_in_site_packages(virtualenv):
+def patch_dist_in_site_packages(virtualenv: VirtualEnvironment) -> None:
     # Since the tests are run from a virtualenv, and to avoid the "Will not
     # install to the usersite because it will lack sys.path precedence..."
     # error: Monkey patch `pip._internal.utils.misc.dist_in_site_packages`
@@ -136,7 +143,9 @@ def dist_in_site_packages(dist):
 
 @pytest.mark.incompatible_with_test_venv
 @pytest.mark.usefixtures("patch_dist_in_site_packages")
-def test_new_resolver_install_user_reinstall_global_site(script):
+def test_new_resolver_install_user_reinstall_global_site(
+    script: PipTestEnvironment,
+) -> None:
     """
     Specifying --force-reinstall makes a different version in user site,
     ignoring the matching installation in global site.
@@ -170,7 +179,9 @@ def test_new_resolver_install_user_reinstall_global_site(script):
 
 @pytest.mark.incompatible_with_test_venv
 @pytest.mark.usefixtures("patch_dist_in_site_packages")
-def test_new_resolver_install_user_conflict_in_global_site(script):
+def test_new_resolver_install_user_conflict_in_global_site(
+    script: PipTestEnvironment,
+) -> None:
     """
     Installing a different version in user site should ignore an existing
     different version in global site, and simply add to the user site.
@@ -206,7 +217,9 @@ def test_new_resolver_install_user_conflict_in_global_site(script):
 
 @pytest.mark.incompatible_with_test_venv
 @pytest.mark.usefixtures("patch_dist_in_site_packages")
-def test_new_resolver_install_user_conflict_in_global_and_user_sites(script):
+def test_new_resolver_install_user_conflict_in_global_and_user_sites(
+    script: PipTestEnvironment,
+) -> None:
     """
     Installing a different version in user site should ignore an existing
     different version in global site, but still upgrade the user site.
diff --git a/tests/functional/test_no_color.py b/tests/functional/test_no_color.py
index c9f86276170..9ead9996ad8 100644
--- a/tests/functional/test_no_color.py
+++ b/tests/functional/test_no_color.py
@@ -6,8 +6,10 @@
 
 import pytest
 
+from tests.lib import PipTestEnvironment
 
-def test_no_color(script):
+
+def test_no_color(script: PipTestEnvironment) -> None:
     """Ensure colour output disabled when --no-color is passed."""
     # Using 'script' in this test allows for transparently testing pip's output
     # since pip is smart enough to disable colour output when piped, which is
@@ -22,7 +24,7 @@ def test_no_color(script):
         '--command "pip uninstall {} noSuchPackage"'
     )
 
-    def get_run_output(option):
+    def get_run_output(option: str) -> str:
         cmd = command.format(option)
         proc = subprocess.Popen(
             cmd,
diff --git a/tests/functional/test_pep517.py b/tests/functional/test_pep517.py
index 7d1dd7400b7..6dd8e2be533 100644
--- a/tests/functional/test_pep517.py
+++ b/tests/functional/test_pep517.py
@@ -1,16 +1,24 @@
+from typing import Any, Dict, List, Optional, Tuple
+
 import pytest
 import tomli_w
 
 from pip._internal.build_env import BuildEnvironment
 from pip._internal.req import InstallRequirement
-from tests.lib import make_test_finder, path_to_url
+from tests.lib import PipTestEnvironment, TestData, make_test_finder, path_to_url
+from tests.lib.path import Path
 
 
-def make_project(tmpdir, requires=None, backend=None, backend_path=None):
+def make_project(
+    tmpdir: Path,
+    requires: Optional[List[str]] = None,
+    backend: Optional[str] = None,
+    backend_path: Optional[List[str]] = None,
+) -> Path:
     requires = requires or []
     project_dir = tmpdir / "project"
     project_dir.mkdir()
-    buildsys = {"requires": requires}
+    buildsys: Dict[str, Any] = {"requires": requires}
     if backend:
         buildsys["build-backend"] = backend
     if backend_path:
@@ -20,7 +28,7 @@ def make_project(tmpdir, requires=None, backend=None, backend_path=None):
     return project_dir
 
 
-def test_backend(tmpdir, data):
+def test_backend(tmpdir: Path, data: TestData) -> None:
     """Check we can call a requirement's backend successfully"""
     project_dir = make_project(tmpdir, backend="dummy_backend")
     req = InstallRequirement(None, None)
@@ -33,6 +41,7 @@ def test_backend(tmpdir, data):
     assert not conflicting and not missing
     assert hasattr(req.pep517_backend, "build_wheel")
     with env:
+        assert req.pep517_backend is not None
         assert req.pep517_backend.build_wheel("dir") == "Backend called"
 
 
@@ -46,7 +55,7 @@ def build_wheel(
 """
 
 
-def test_backend_path(tmpdir, data):
+def test_backend_path(tmpdir: Path, data: TestData) -> None:
     """Check we can call a backend inside the project"""
     project_dir = make_project(tmpdir, backend="dummy_backend", backend_path=["."])
     (project_dir / "dummy_backend.py").write_text(dummy_backend_code)
@@ -57,10 +66,11 @@ def test_backend_path(tmpdir, data):
     env = BuildEnvironment()
     assert hasattr(req.pep517_backend, "build_wheel")
     with env:
+        assert req.pep517_backend is not None
         assert req.pep517_backend.build_wheel("dir") == "Backend called"
 
 
-def test_backend_path_and_dep(tmpdir, data):
+def test_backend_path_and_dep(tmpdir: Path, data: TestData) -> None:
     """Check we can call a requirement's backend successfully"""
     project_dir = make_project(
         tmpdir, backend="dummy_internal_backend", backend_path=["."]
@@ -77,10 +87,13 @@ def test_backend_path_and_dep(tmpdir, data):
 
     assert hasattr(req.pep517_backend, "build_wheel")
     with env:
+        assert req.pep517_backend is not None
         assert req.pep517_backend.build_wheel("dir") == "Backend called"
 
 
-def test_pep517_install(script, tmpdir, data):
+def test_pep517_install(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     """Check we can build with a custom backend"""
     project_dir = make_project(
         tmpdir, requires=["test_backend"], backend="test_backend"
@@ -89,7 +102,9 @@ def test_pep517_install(script, tmpdir, data):
     result.assert_installed("project", editable=False)
 
 
-def test_pep517_install_with_reqs(script, tmpdir, data):
+def test_pep517_install_with_reqs(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     """Backend generated requirements are installed in the build env"""
     project_dir = make_project(
         tmpdir, requires=["test_backend"], backend="test_backend"
@@ -101,7 +116,9 @@ def test_pep517_install_with_reqs(script, tmpdir, data):
     result.assert_installed("project", editable=False)
 
 
-def test_no_use_pep517_without_setup_py(script, tmpdir, data):
+def test_no_use_pep517_without_setup_py(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     """Using --no-use-pep517 requires setup.py"""
     project_dir = make_project(
         tmpdir, requires=["test_backend"], backend="test_backend"
@@ -118,7 +135,9 @@ def test_no_use_pep517_without_setup_py(script, tmpdir, data):
     assert "project does not have a setup.py" in result.stderr
 
 
-def test_conflicting_pep517_backend_requirements(script, tmpdir, data):
+def test_conflicting_pep517_backend_requirements(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     project_dir = make_project(
         tmpdir, requires=["test_backend", "simplewheel==1.0"], backend="test_backend"
     )
@@ -141,7 +160,9 @@ def test_conflicting_pep517_backend_requirements(script, tmpdir, data):
     assert result.returncode != 0 and msg in result.stderr, str(result)
 
 
-def test_pep517_backend_requirements_already_satisfied(script, tmpdir, data):
+def test_pep517_backend_requirements_already_satisfied(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     project_dir = make_project(
         tmpdir, requires=["test_backend", "simplewheel==1.0"], backend="test_backend"
     )
@@ -158,7 +179,9 @@ def test_pep517_backend_requirements_already_satisfied(script, tmpdir, data):
     assert "Installing backend dependencies:" not in result.stdout
 
 
-def test_pep517_install_with_no_cache_dir(script, tmpdir, data):
+def test_pep517_install_with_no_cache_dir(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData
+) -> None:
     """Check builds with a custom backends work, even with no cache."""
     project_dir = make_project(
         tmpdir, requires=["test_backend"], backend="test_backend"
@@ -174,13 +197,15 @@ def test_pep517_install_with_no_cache_dir(script, tmpdir, data):
     result.assert_installed("project", editable=False)
 
 
-def make_pyproject_with_setup(tmpdir, build_system=True, set_backend=True):
+def make_pyproject_with_setup(
+    tmpdir: Path, build_system: bool = True, set_backend: bool = True
+) -> Tuple[Path, str]:
     project_dir = tmpdir / "project"
     project_dir.mkdir()
     setup_script = "from setuptools import setup\n"
     expect_script_dir_on_path = True
     if build_system:
-        buildsys = {
+        buildsys: Dict[str, Any] = {
             "requires": ["setuptools", "wheel"],
         }
         if set_backend:
@@ -212,7 +237,9 @@ def make_pyproject_with_setup(tmpdir, build_system=True, set_backend=True):
     return project_dir, "pep517_test"
 
 
-def test_no_build_system_section(script, tmpdir, data, common_wheels):
+def test_no_build_system_section(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData, common_wheels: Path
+) -> None:
     """Check builds with setup.py, pyproject.toml, but no build-system section."""
     project_dir, name = make_pyproject_with_setup(tmpdir, build_system=False)
     result = script.pip(
@@ -226,7 +253,9 @@ def test_no_build_system_section(script, tmpdir, data, common_wheels):
     result.assert_installed(name, editable=False)
 
 
-def test_no_build_backend_entry(script, tmpdir, data, common_wheels):
+def test_no_build_backend_entry(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData, common_wheels: Path
+) -> None:
     """Check builds with setup.py, pyproject.toml, but no build-backend entry."""
     project_dir, name = make_pyproject_with_setup(tmpdir, set_backend=False)
     result = script.pip(
@@ -240,7 +269,9 @@ def test_no_build_backend_entry(script, tmpdir, data, common_wheels):
     result.assert_installed(name, editable=False)
 
 
-def test_explicit_setuptools_backend(script, tmpdir, data, common_wheels):
+def test_explicit_setuptools_backend(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData, common_wheels: Path
+) -> None:
     """Check builds with setup.py, pyproject.toml, and a build-backend entry."""
     project_dir, name = make_pyproject_with_setup(tmpdir)
     result = script.pip(
@@ -255,7 +286,9 @@ def test_explicit_setuptools_backend(script, tmpdir, data, common_wheels):
 
 
 @pytest.mark.network
-def test_pep517_and_build_options(script, tmpdir, data, common_wheels):
+def test_pep517_and_build_options(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData, common_wheels: Path
+) -> None:
     """Backend generated requirements are installed in the build env"""
     project_dir, name = make_pyproject_with_setup(tmpdir)
     result = script.pip(
@@ -273,7 +306,9 @@ def test_pep517_and_build_options(script, tmpdir, data, common_wheels):
 
 
 @pytest.mark.network
-def test_pep517_and_global_options(script, tmpdir, data, common_wheels):
+def test_pep517_and_global_options(
+    script: PipTestEnvironment, tmpdir: Path, data: TestData, common_wheels: Path
+) -> None:
     """Backend generated requirements are installed in the build env"""
     project_dir, name = make_pyproject_with_setup(tmpdir)
     result = script.pip(
diff --git a/tests/functional/test_pep660.py b/tests/functional/test_pep660.py
index 52549f1d3f1..c55fb80d37b 100644
--- a/tests/functional/test_pep660.py
+++ b/tests/functional/test_pep660.py
@@ -1,8 +1,12 @@
 import os
+from typing import Any, Dict
 
+import pytest
 import tomli_w
 
 from pip._internal.utils.urls import path_to_url
+from tests.lib import PipTestEnvironment
+from tests.lib.path import Path
 
 SETUP_PY = """
 from setuptools import setup
@@ -59,7 +63,9 @@ def build_editable(wheel_directory, config_settings=None, metadata_directory=Non
 # fmt: on
 
 
-def _make_project(tmpdir, backend_code, with_setup_py, with_pyproject=True):
+def _make_project(
+    tmpdir: Path, backend_code: str, with_setup_py: bool, with_pyproject: bool = True
+) -> Path:
     project_dir = tmpdir / "project"
     project_dir.mkdir()
     project_dir.joinpath("setup.cfg").write_text(SETUP_CFG)
@@ -67,7 +73,7 @@ def _make_project(tmpdir, backend_code, with_setup_py, with_pyproject=True):
         project_dir.joinpath("setup.py").write_text(SETUP_PY)
     if backend_code:
         assert with_pyproject
-        buildsys = {"requires": ["setuptools", "wheel"]}
+        buildsys: Dict[str, Any] = {"requires": ["setuptools", "wheel"]}
         buildsys["build-backend"] = "test_backend"
         buildsys["backend-path"] = ["."]
         data = tomli_w.dumps({"build-system": buildsys})
@@ -79,17 +85,18 @@ def _make_project(tmpdir, backend_code, with_setup_py, with_pyproject=True):
     return project_dir
 
 
-def _assert_hook_called(project_dir, hook):
+def _assert_hook_called(project_dir: Path, hook: str) -> None:
     log = project_dir.joinpath("log.txt").read_text()
     assert f":{hook} called" in log, f"{hook} has not been called"
 
 
-def _assert_hook_not_called(project_dir, hook):
+def _assert_hook_not_called(project_dir: Path, hook: str) -> None:
     log = project_dir.joinpath("log.txt").read_text()
     assert f":{hook} called" not in log, f"{hook} should not have been called"
 
 
-def test_install_pep517_basic(tmpdir, script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_install_pep517_basic(tmpdir: Path, script: PipTestEnvironment) -> None:
     """
     Check that the test harness we have in this file is sane.
     """
@@ -104,7 +111,8 @@ def test_install_pep517_basic(tmpdir, script, with_wheel):
     _assert_hook_called(project_dir, "build_wheel")
 
 
-def test_install_pep660_basic(tmpdir, script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_install_pep660_basic(tmpdir: Path, script: PipTestEnvironment) -> None:
     """
     Test with backend that supports build_editable.
     """
@@ -124,7 +132,10 @@ def test_install_pep660_basic(tmpdir, script, with_wheel):
     ), "a .egg-link file should not have been created"
 
 
-def test_install_no_pep660_setup_py_fallback(tmpdir, script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_install_no_pep660_setup_py_fallback(
+    tmpdir: Path, script: PipTestEnvironment
+) -> None:
     """
     Test that we fall back to setuptools develop when using a backend that
     does not support build_editable. Since there is a pyproject.toml,
@@ -146,7 +157,10 @@ def test_install_no_pep660_setup_py_fallback(tmpdir, script, with_wheel):
     ), "a .egg-link file should have been created"
 
 
-def test_install_no_pep660_setup_cfg_fallback(tmpdir, script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_install_no_pep660_setup_cfg_fallback(
+    tmpdir: Path, script: PipTestEnvironment
+) -> None:
     """
     Test that we fall back to setuptools develop when using a backend that
     does not support build_editable. Since there is a pyproject.toml,
@@ -169,7 +183,8 @@ def test_install_no_pep660_setup_cfg_fallback(tmpdir, script, with_wheel):
     ), ".egg-link file should have been created"
 
 
-def test_wheel_editable_pep660_basic(tmpdir, script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_wheel_editable_pep660_basic(tmpdir: Path, script: PipTestEnvironment) -> None:
     """
     Test 'pip wheel' of an editable pep 660 project.
     It must *not* call prepare_metadata_for_build_editable.
@@ -192,7 +207,10 @@ def test_wheel_editable_pep660_basic(tmpdir, script, with_wheel):
     assert len(os.listdir(str(wheel_dir))) == 1, "a wheel should have been created"
 
 
-def test_download_editable_pep660_basic(tmpdir, script, with_wheel):
+@pytest.mark.usefixtures("with_wheel")
+def test_download_editable_pep660_basic(
+    tmpdir: Path, script: PipTestEnvironment
+) -> None:
     """
     Test 'pip download' of an editable pep 660 project.
     It must *not* call prepare_metadata_for_build_editable.
diff --git a/tests/functional/test_requests.py b/tests/functional/test_requests.py
index b6bece867ed..0fbc4ae0e36 100644
--- a/tests/functional/test_requests.py
+++ b/tests/functional/test_requests.py
@@ -1,8 +1,10 @@
 import pytest
 
+from tests.lib import PipTestEnvironment
+
 
 @pytest.mark.network
-def test_timeout(script):
+def test_timeout(script: PipTestEnvironment) -> None:
     result = script.pip(
         "--timeout",
         "0.0001",
diff --git a/tests/functional/test_search.py b/tests/functional/test_search.py
index 000fbb79568..3f784e5dd1c 100644
--- a/tests/functional/test_search.py
+++ b/tests/functional/test_search.py
@@ -1,4 +1,5 @@
 import logging
+from typing import TYPE_CHECKING, Dict, List
 from unittest import mock
 
 import pytest
@@ -6,9 +7,13 @@
 from pip._internal.cli.status_codes import NO_MATCHES_FOUND, SUCCESS
 from pip._internal.commands import create_command
 from pip._internal.commands.search import highest_version, print_results, transform_hits
+from tests.lib import PipTestEnvironment
 
+if TYPE_CHECKING:
+    from pip._internal.commands.search import TransformedHit
 
-def test_version_compare():
+
+def test_version_compare() -> None:
     """
     Test version comparison.
 
@@ -17,12 +22,12 @@ def test_version_compare():
     assert highest_version(["1.0a1", "1.0"]) == "1.0"
 
 
-def test_pypi_xml_transformation():
+def test_pypi_xml_transformation() -> None:
     """
     Test transformation of data structures (PyPI xmlrpc to custom list).
 
     """
-    pypi_hits = [
+    pypi_hits: List[Dict[str, str]] = [
         {
             "name": "foo",
             "summary": "foo summary",
@@ -34,13 +39,13 @@ def test_pypi_xml_transformation():
             "version": "2.0",
         },
         {
-            "_pypi_ordering": 50,
+            "_pypi_ordering": 50,  # type: ignore[dict-item]
             "name": "bar",
             "summary": "bar summary",
             "version": "1.0",
         },
     ]
-    expected = [
+    expected: List["TransformedHit"] = [
         {
             "versions": ["1.0", "2.0"],
             "name": "foo",
@@ -57,7 +62,7 @@ def test_pypi_xml_transformation():
 
 @pytest.mark.network
 @pytest.mark.search
-def test_basic_search(script):
+def test_basic_search(script: PipTestEnvironment) -> None:
     """
     End to end test of search command.
 
@@ -76,7 +81,7 @@ def test_basic_search(script):
     ),
 )
 @pytest.mark.search
-def test_multiple_search(script):
+def test_multiple_search(script: PipTestEnvironment) -> None:
     """
     Test searching for multiple packages at once.
 
@@ -87,7 +92,7 @@ def test_multiple_search(script):
 
 
 @pytest.mark.search
-def test_search_missing_argument(script):
+def test_search_missing_argument(script: PipTestEnvironment) -> None:
     """
     Test missing required argument for search
     """
@@ -97,7 +102,7 @@ def test_search_missing_argument(script):
 
 @pytest.mark.network
 @pytest.mark.search
-def test_run_method_should_return_success_when_find_packages():
+def test_run_method_should_return_success_when_find_packages() -> None:
     """
     Test SearchCommand.run for found package
     """
@@ -111,7 +116,7 @@ def test_run_method_should_return_success_when_find_packages():
 
 @pytest.mark.network
 @pytest.mark.search
-def test_run_method_should_return_no_matches_found_when_does_not_find_pkgs():
+def test_run_method_should_return_no_matches_found_when_does_not_find_pkgs() -> None:
     """
     Test SearchCommand.run for no matches
     """
@@ -125,7 +130,9 @@ def test_run_method_should_return_no_matches_found_when_does_not_find_pkgs():
 
 @pytest.mark.network
 @pytest.mark.search
-def test_search_should_exit_status_code_zero_when_find_packages(script):
+def test_search_should_exit_status_code_zero_when_find_packages(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test search exit status code for package found
     """
@@ -135,7 +142,9 @@ def test_search_should_exit_status_code_zero_when_find_packages(script):
 
 @pytest.mark.network
 @pytest.mark.search
-def test_search_exit_status_code_when_finds_no_package(script):
+def test_search_exit_status_code_when_finds_no_package(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test search exit status code for no matches
     """
@@ -144,11 +153,13 @@ def test_search_exit_status_code_when_finds_no_package(script):
 
 
 @pytest.mark.search
-def test_latest_prerelease_install_message(caplog, monkeypatch):
+def test_latest_prerelease_install_message(
+    caplog: pytest.LogCaptureFixture, monkeypatch: pytest.MonkeyPatch
+) -> None:
     """
     Test documentation for installing pre-release packages is displayed
     """
-    hits = [
+    hits: List["TransformedHit"] = [
         {
             "name": "ni",
             "summary": "For knights who say Ni!",
@@ -171,11 +182,13 @@ def test_latest_prerelease_install_message(caplog, monkeypatch):
 
 
 @pytest.mark.search
-def test_search_print_results_should_contain_latest_versions(caplog):
+def test_search_print_results_should_contain_latest_versions(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
     """
     Test that printed search results contain the latest package versions
     """
-    hits = [
+    hits: List["TransformedHit"] = [
         {
             "name": "testlib1",
             "summary": "Test library 1.",
diff --git a/tests/functional/test_show.py b/tests/functional/test_show.py
index 454130bb249..a704911e643 100644
--- a/tests/functional/test_show.py
+++ b/tests/functional/test_show.py
@@ -1,4 +1,5 @@
 import os
+import pathlib
 import re
 
 from pip import __version__
@@ -7,10 +8,10 @@
     write_installed_files_from_setuptools_record,
 )
 from pip._internal.utils.unpacking import untar_file
-from tests.lib import create_test_package_with_setup
+from tests.lib import PipTestEnvironment, TestData, create_test_package_with_setup
 
 
-def test_basic_show(script):
+def test_basic_show(script: PipTestEnvironment) -> None:
     """
     Test end to end test for show command.
     """
@@ -23,7 +24,7 @@ def test_basic_show(script):
     assert "Requires: " in lines
 
 
-def test_show_with_files_not_found(script, data):
+def test_show_with_files_not_found(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test for show command with installed files listing enabled and
     installed-files.txt not found.
@@ -41,7 +42,7 @@ def test_show_with_files_not_found(script, data):
     assert "Cannot locate RECORD or installed-files.txt" in lines
 
 
-def test_show_with_files_from_wheel(script, data):
+def test_show_with_files_from_wheel(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test that a wheel's files can be listed.
     """
@@ -55,7 +56,9 @@ def test_show_with_files_from_wheel(script, data):
     assert f"  simpledist{os.sep}__init__.py" in lines[6:]
 
 
-def test_show_with_files_from_legacy(tmp_path, script, data):
+def test_show_with_files_from_legacy(
+    tmp_path: pathlib.Path, script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test listing files in the show command (legacy installed-files.txt).
     """
@@ -87,7 +90,7 @@ def test_show_with_files_from_legacy(tmp_path, script, data):
     assert f"  simple{os.sep}__init__.py" in lines[6:]
 
 
-def test_missing_argument(script):
+def test_missing_argument(script: PipTestEnvironment) -> None:
     """
     Test show command with no arguments.
     """
@@ -95,7 +98,7 @@ def test_missing_argument(script):
     assert "ERROR: Please provide a package name or names." in result.stderr
 
 
-def test_find_package_not_found():
+def test_find_package_not_found() -> None:
     """
     Test trying to get info about a nonexistent package.
     """
@@ -103,7 +106,7 @@ def test_find_package_not_found():
     assert len(list(result)) == 0
 
 
-def test_report_single_not_found(script):
+def test_report_single_not_found(script: PipTestEnvironment) -> None:
     """
     Test passing one name and that isn't found.
     """
@@ -117,7 +120,7 @@ def test_report_single_not_found(script):
     assert not result.stdout.splitlines()
 
 
-def test_report_mixed_not_found(script):
+def test_report_mixed_not_found(script: PipTestEnvironment) -> None:
     """
     Test passing a mixture of found and not-found names.
     """
@@ -129,7 +132,7 @@ def test_report_mixed_not_found(script):
     assert "Name: pip" in lines
 
 
-def test_search_any_case():
+def test_search_any_case() -> None:
     """
     Search for a package in any case.
 
@@ -139,7 +142,7 @@ def test_search_any_case():
     assert result[0].name == "pip"
 
 
-def test_more_than_one_package():
+def test_more_than_one_package() -> None:
     """
     Search for more than one package.
 
@@ -148,7 +151,7 @@ def test_more_than_one_package():
     assert len(result) == 3
 
 
-def test_show_verbose_with_classifiers(script):
+def test_show_verbose_with_classifiers(script: PipTestEnvironment) -> None:
     """
     Test that classifiers can be listed
     """
@@ -159,7 +162,7 @@ def test_show_verbose_with_classifiers(script):
     assert "Intended Audience :: Developers" in result.stdout
 
 
-def test_show_verbose_installer(script, data):
+def test_show_verbose_installer(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test that the installer is shown (this currently needs a wheel install)
     """
@@ -171,7 +174,7 @@ def test_show_verbose_installer(script, data):
     assert "Installer: pip" in lines
 
 
-def test_show_verbose(script):
+def test_show_verbose(script: PipTestEnvironment) -> None:
     """
     Test end to end test for verbose show command.
     """
@@ -183,7 +186,7 @@ def test_show_verbose(script):
     assert "Classifiers:" in lines
 
 
-def test_all_fields(script):
+def test_all_fields(script: PipTestEnvironment) -> None:
     """
     Test that all the fields are present
     """
@@ -205,7 +208,7 @@ def test_all_fields(script):
     assert actual == expected
 
 
-def test_pip_show_is_short(script):
+def test_pip_show_is_short(script: PipTestEnvironment) -> None:
     """
     Test that pip show stays short
     """
@@ -214,7 +217,7 @@ def test_pip_show_is_short(script):
     assert len(lines) <= 10
 
 
-def test_pip_show_divider(script, data):
+def test_pip_show_divider(script: PipTestEnvironment, data: TestData) -> None:
     """
     Expect a divider between packages
     """
@@ -224,7 +227,9 @@ def test_pip_show_divider(script, data):
     assert "---" in lines
 
 
-def test_package_name_is_canonicalized(script, data):
+def test_package_name_is_canonicalized(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.pip("install", "pip-test-package", "--no-index", "-f", data.packages)
 
     dash_show_result = script.pip("show", "pip-test-package")
@@ -234,7 +239,9 @@ def test_package_name_is_canonicalized(script, data):
     assert underscore_upper_show_result.stdout == dash_show_result.stdout
 
 
-def test_show_required_by_packages_basic(script, data):
+def test_show_required_by_packages_basic(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test that installed packages that depend on this package are shown
     """
@@ -248,7 +255,9 @@ def test_show_required_by_packages_basic(script, data):
     assert "Required-by: requires-simple" in lines
 
 
-def test_show_required_by_packages_capitalized(script, data):
+def test_show_required_by_packages_capitalized(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test that the installed packages which depend on a package are shown
     where the package has a capital letter
@@ -263,7 +272,9 @@ def test_show_required_by_packages_capitalized(script, data):
     assert "Required-by: Requires-Capitalized" in lines
 
 
-def test_show_required_by_packages_requiring_capitalized(script, data):
+def test_show_required_by_packages_requiring_capitalized(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test that the installed packages which depend on a package are shown
     where the package has a name with a mix of
@@ -282,7 +293,7 @@ def test_show_required_by_packages_requiring_capitalized(script, data):
     assert "Required-by: requires-requires-capitalized" in lines
 
 
-def test_show_skip_work_dir_pkg(script):
+def test_show_skip_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that show should not include package
     present in working directory
@@ -297,7 +308,7 @@ def test_show_skip_work_dir_pkg(script):
     assert "WARNING: Package(s) not found: simple" in result.stderr
 
 
-def test_show_include_work_dir_pkg(script):
+def test_show_include_work_dir_pkg(script: PipTestEnvironment) -> None:
     """
     Test that show should include package in working directory
     if working directory is added in PYTHONPATH
diff --git a/tests/functional/test_uninstall.py b/tests/functional/test_uninstall.py
index 3adaf438b82..458ca9190a5 100644
--- a/tests/functional/test_uninstall.py
+++ b/tests/functional/test_uninstall.py
@@ -4,19 +4,26 @@
 import textwrap
 from os.path import join, normpath
 from tempfile import mkdtemp
+from typing import Any
 from unittest.mock import Mock
 
 import pytest
 
 from pip._internal.req.constructors import install_req_from_line
 from pip._internal.utils.misc import rmtree
-from tests.lib import assert_all_changes, create_test_package_with_setup, need_svn
+from tests.lib import (
+    PipTestEnvironment,
+    TestData,
+    assert_all_changes,
+    create_test_package_with_setup,
+    need_svn,
+)
 from tests.lib.local_repos import local_checkout, local_repo
 from tests.lib.path import Path
 
 
 @pytest.mark.network
-def test_basic_uninstall(script):
+def test_basic_uninstall(script: PipTestEnvironment) -> None:
     """
     Test basic install and uninstall.
 
@@ -30,7 +37,7 @@ def test_basic_uninstall(script):
     assert_all_changes(result, result2, [script.venv / "build", "cache"])
 
 
-def test_basic_uninstall_distutils(script):
+def test_basic_uninstall_distutils(script: PipTestEnvironment) -> None:
     """
     Test basic install and uninstall.
 
@@ -62,7 +69,7 @@ def test_basic_uninstall_distutils(script):
 
 
 @pytest.mark.network
-def test_basic_uninstall_with_scripts(script):
+def test_basic_uninstall_with_scripts(script: PipTestEnvironment) -> None:
     """
     Uninstall an easy_installed package with scripts.
 
@@ -83,7 +90,9 @@ def test_basic_uninstall_with_scripts(script):
 
 
 @pytest.mark.parametrize("name", ["GTrolls.tar.gz", "https://guyto.com/archives/"])
-def test_uninstall_invalid_parameter(script, caplog, name):
+def test_uninstall_invalid_parameter(
+    script: PipTestEnvironment, caplog: pytest.LogCaptureFixture, name: str
+) -> None:
     result = script.pip("uninstall", name, "-y", expect_error=True)
     expected_message = (
         f"Invalid requirement: '{name}' ignored -"
@@ -93,7 +102,7 @@ def test_uninstall_invalid_parameter(script, caplog, name):
 
 
 @pytest.mark.network
-def test_uninstall_easy_install_after_import(script):
+def test_uninstall_easy_install_after_import(script: PipTestEnvironment) -> None:
     """
     Uninstall an easy_installed package after it's been imported
 
@@ -118,7 +127,7 @@ def test_uninstall_easy_install_after_import(script):
 
 
 @pytest.mark.network
-def test_uninstall_trailing_newline(script):
+def test_uninstall_trailing_newline(script: PipTestEnvironment) -> None:
     """
     Uninstall behaves appropriately if easy-install.pth
     lacks a trailing newline
@@ -153,7 +162,7 @@ def test_uninstall_trailing_newline(script):
 
 
 @pytest.mark.network
-def test_basic_uninstall_namespace_package(script):
+def test_basic_uninstall_namespace_package(script: PipTestEnvironment) -> None:
     """
     Uninstall a distribution with a namespace package without clobbering
     the namespace and everything in it.
@@ -170,7 +179,9 @@ def test_basic_uninstall_namespace_package(script):
     )
 
 
-def test_uninstall_overlapping_package(script, data):
+def test_uninstall_overlapping_package(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Uninstalling a distribution that adds modules to a pre-existing package
     should only remove those added modules, not the rest of the existing
@@ -210,7 +221,9 @@ def test_uninstall_overlapping_package(script, data):
 @pytest.mark.parametrize(
     "console_scripts", ["test_ = distutils_install", "test_:test_ = distutils_install"]
 )
-def test_uninstall_entry_point_colon_in_name(script, console_scripts):
+def test_uninstall_entry_point_colon_in_name(
+    script: PipTestEnvironment, console_scripts: str
+) -> None:
     """
     Test uninstall package with two or more entry points in the same section,
     whose name contain a colon.
@@ -242,7 +255,7 @@ def test_uninstall_entry_point_colon_in_name(script, console_scripts):
     script.assert_not_installed("ep-install")
 
 
-def test_uninstall_gui_scripts(script):
+def test_uninstall_gui_scripts(script: PipTestEnvironment) -> None:
     """
     Make sure that uninstall removes gui scripts
     """
@@ -266,7 +279,7 @@ def test_uninstall_gui_scripts(script):
     assert not script_name.exists()
 
 
-def test_uninstall_console_scripts(script):
+def test_uninstall_console_scripts(script: PipTestEnvironment) -> None:
     """
     Test uninstalling a package with more files (console_script entry points,
     extra directories).
@@ -291,7 +304,7 @@ def test_uninstall_console_scripts(script):
     )
 
 
-def test_uninstall_console_scripts_uppercase_name(script):
+def test_uninstall_console_scripts_uppercase_name(script: PipTestEnvironment) -> None:
     """
     Test uninstalling console script with uppercase character.
     """
@@ -315,7 +328,7 @@ def test_uninstall_console_scripts_uppercase_name(script):
 
 
 @pytest.mark.network
-def test_uninstall_easy_installed_console_scripts(script):
+def test_uninstall_easy_installed_console_scripts(script: PipTestEnvironment) -> None:
     """
     Test uninstalling package with console_scripts that is easy_installed.
     """
@@ -340,7 +353,7 @@ def test_uninstall_easy_installed_console_scripts(script):
 @pytest.mark.xfail
 @pytest.mark.network
 @need_svn
-def test_uninstall_editable_from_svn(script, tmpdir):
+def test_uninstall_editable_from_svn(script: PipTestEnvironment, tmpdir: Path) -> None:
     """
     Test uninstalling an editable installation from svn.
     """
@@ -366,7 +379,9 @@ def test_uninstall_editable_from_svn(script, tmpdir):
 
 
 @pytest.mark.network
-def test_uninstall_editable_with_source_outside_venv(script, tmpdir):
+def test_uninstall_editable_with_source_outside_venv(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test uninstalling editable install from existing source outside the venv.
     """
@@ -383,10 +398,10 @@ def test_uninstall_editable_with_source_outside_venv(script, tmpdir):
 
 
 def _test_uninstall_editable_with_source_outside_venv(
-    script,
-    tmpdir,
-    temp_pkg_dir,
-):
+    script: PipTestEnvironment,
+    tmpdir: Path,
+    temp_pkg_dir: str,
+) -> None:
     result = script.run(
         "git",
         "clone",
@@ -407,7 +422,7 @@ def _test_uninstall_editable_with_source_outside_venv(
 @pytest.mark.xfail
 @pytest.mark.network
 @need_svn
-def test_uninstall_from_reqs_file(script, tmpdir):
+def test_uninstall_from_reqs_file(script: PipTestEnvironment, tmpdir: Path) -> None:
     """
     Test uninstall from a requirements file.
 
@@ -453,7 +468,7 @@ def test_uninstall_from_reqs_file(script, tmpdir):
     )
 
 
-def test_uninstallpathset_no_paths(caplog):
+def test_uninstallpathset_no_paths(caplog: pytest.LogCaptureFixture) -> None:
     """
     Test UninstallPathSet logs notification when there are no paths to
     uninstall
@@ -471,7 +486,9 @@ def test_uninstallpathset_no_paths(caplog):
     assert "Can't uninstall 'pip'. No files were found to uninstall." in caplog.text
 
 
-def test_uninstall_non_local_distutils(caplog, monkeypatch, tmpdir):
+def test_uninstall_non_local_distutils(
+    caplog: pytest.LogCaptureFixture, monkeypatch: pytest.MonkeyPatch, tmpdir: Path
+) -> None:
     einfo = tmpdir.joinpath("thing-1.0.egg-info")
     with open(einfo, "wb"):
         pass
@@ -491,7 +508,7 @@ def test_uninstall_non_local_distutils(caplog, monkeypatch, tmpdir):
     assert os.path.exists(einfo)
 
 
-def test_uninstall_wheel(script, data):
+def test_uninstall_wheel(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test uninstalling a wheel
     """
@@ -515,7 +532,9 @@ def test_uninstall_wheel(script, data):
         "MegaCorp Cloud Install-O-Matic",
     ],
 )
-def test_uninstall_without_record_fails(script, data, installer):
+def test_uninstall_without_record_fails(
+    script: PipTestEnvironment, data: TestData, installer: Any
+) -> None:
     """
     Test uninstalling a package installed without RECORD
     """
@@ -562,7 +581,9 @@ def test_uninstall_without_record_fails(script, data, installer):
 
 
 @pytest.mark.skipif("sys.platform == 'win32'")
-def test_uninstall_with_symlink(script, data, tmpdir):
+def test_uninstall_with_symlink(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test uninstalling a wheel, with an additional symlink
     https://github.com/pypa/pip/issues/6892
@@ -583,7 +604,9 @@ def test_uninstall_with_symlink(script, data, tmpdir):
     assert symlink_target.stat().st_mode == st_mode
 
 
-def test_uninstall_setuptools_develop_install(script, data):
+def test_uninstall_setuptools_develop_install(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Try uninstall after setup.py develop followed of setup.py install"""
     pkg_path = data.packages.joinpath("FSPkg")
     script.run("python", "setup.py", "develop", expect_stderr=True, cwd=pkg_path)
@@ -599,7 +622,9 @@ def test_uninstall_setuptools_develop_install(script, data):
     script.assert_not_installed("FSPkg")
 
 
-def test_uninstall_editable_and_pip_install(script, data):
+def test_uninstall_editable_and_pip_install(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Try uninstall after pip install -e after pip install"""
     # SETUPTOOLS_SYS_PATH_TECHNIQUE=raw removes the assumption that `-e`
     # installs are always higher priority than regular installs.
@@ -623,7 +648,9 @@ def test_uninstall_editable_and_pip_install(script, data):
     script.assert_not_installed("FSPkg")
 
 
-def test_uninstall_editable_and_pip_install_easy_install_remove(script, data):
+def test_uninstall_editable_and_pip_install_easy_install_remove(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Try uninstall after pip install -e after pip install
     and removing easy-install.pth"""
     # SETUPTOOLS_SYS_PATH_TECHNIQUE=raw removes the assumption that `-e`
@@ -665,7 +692,9 @@ def test_uninstall_editable_and_pip_install_easy_install_remove(script, data):
     os.rename(pip_test_pth, easy_install_pth)
 
 
-def test_uninstall_ignores_missing_packages(script, data):
+def test_uninstall_ignores_missing_packages(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Uninstall of a non existent package prints a warning and exits cleanly"""
     result = script.pip(
         "uninstall",
@@ -678,7 +707,9 @@ def test_uninstall_ignores_missing_packages(script, data):
     assert result.returncode == 0, "Expected clean exit"
 
 
-def test_uninstall_ignores_missing_packages_and_uninstalls_rest(script, data):
+def test_uninstall_ignores_missing_packages_and_uninstalls_rest(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.pip_install_local("simple")
     result = script.pip(
         "uninstall",
diff --git a/tests/functional/test_uninstall_user.py b/tests/functional/test_uninstall_user.py
index b77cea2120a..6d48fe1627a 100644
--- a/tests/functional/test_uninstall_user.py
+++ b/tests/functional/test_uninstall_user.py
@@ -7,13 +7,14 @@
 
 from tests.functional.test_install_user import _patch_dist_in_site_packages
 from tests.lib import pyversion  # noqa: F401
-from tests.lib import assert_all_changes
+from tests.lib import PipTestEnvironment, TestData, assert_all_changes
+from tests.lib.venv import VirtualEnvironment
 
 
 @pytest.mark.incompatible_with_test_venv
 class Tests_UninstallUserSite:
     @pytest.mark.network
-    def test_uninstall_from_usersite(self, script):
+    def test_uninstall_from_usersite(self, script: PipTestEnvironment) -> None:
         """
         Test uninstall from usersite
         """
@@ -21,7 +22,9 @@ def test_uninstall_from_usersite(self, script):
         result2 = script.pip("uninstall", "-y", "INITools")
         assert_all_changes(result1, result2, [script.venv / "build", "cache"])
 
-    def test_uninstall_from_usersite_with_dist_in_global_site(self, virtualenv, script):
+    def test_uninstall_from_usersite_with_dist_in_global_site(
+        self, virtualenv: VirtualEnvironment, script: PipTestEnvironment
+    ) -> None:
         """
         Test uninstall from usersite (with same dist in global site)
         """
@@ -50,7 +53,9 @@ def test_uninstall_from_usersite_with_dist_in_global_site(self, virtualenv, scri
         )
         assert isdir(egg_info_folder)
 
-    def test_uninstall_editable_from_usersite(self, script, data):
+    def test_uninstall_editable_from_usersite(
+        self, script: PipTestEnvironment, data: TestData
+    ) -> None:
         """
         Test uninstall editable local user install
         """
diff --git a/tests/functional/test_vcs_bazaar.py b/tests/functional/test_vcs_bazaar.py
index ea91f715068..06f9cbc8107 100644
--- a/tests/functional/test_vcs_bazaar.py
+++ b/tests/functional/test_vcs_bazaar.py
@@ -9,23 +9,23 @@
 
 from pip._internal.vcs.bazaar import Bazaar
 from pip._internal.vcs.versioncontrol import RemoteNotFoundError
-from tests.lib import is_bzr_installed, need_bzr
+from tests.lib import PipTestEnvironment, is_bzr_installed, need_bzr
+from tests.lib.path import Path
 
 
 @pytest.mark.skipif(
     sys.platform == "win32" or "CI" not in os.environ,
     reason="Bazaar is only required under CI",
 )
-def test_ensure_bzr_available():
+def test_ensure_bzr_available() -> None:
     """Make sure that bzr is available when running in CI."""
     assert is_bzr_installed()
 
 
 @need_bzr
-def test_get_remote_url__no_remote(script, tmpdir):
+def test_get_remote_url__no_remote(script: PipTestEnvironment, tmpdir: Path) -> None:
     repo_dir = tmpdir / "temp-repo"
     repo_dir.mkdir()
-    repo_dir = str(repo_dir)
 
     script.run("bzr", "init", repo_dir)
 
diff --git a/tests/functional/test_vcs_git.py b/tests/functional/test_vcs_git.py
index 8f636b30336..928aadd4978 100644
--- a/tests/functional/test_vcs_git.py
+++ b/tests/functional/test_vcs_git.py
@@ -1,22 +1,30 @@
 """
 Contains functional tests of the Git class.
 """
-
 import os
+import pathlib
+from typing import List, Optional, Tuple
 from unittest.mock import patch
 
 import pytest
 
+from pip._internal.utils.misc import HiddenText
 from pip._internal.vcs import vcs
 from pip._internal.vcs.git import Git, RemoteNotFoundError
-from tests.lib import _create_test_package, _git_commit, _test_path_to_file_url
+from tests.lib import (
+    PipTestEnvironment,
+    _create_test_package,
+    _git_commit,
+    _test_path_to_file_url,
+)
+from tests.lib.path import Path
 
 
-def test_get_backend_for_scheme():
+def test_get_backend_for_scheme() -> None:
     assert vcs.get_backend_for_scheme("git+https") is vcs.get_backend("Git")
 
 
-def get_head_sha(script, dest):
+def get_head_sha(script: PipTestEnvironment, dest: str) -> str:
     """Return the HEAD sha."""
     result = script.run("git", "rev-parse", "HEAD", cwd=dest)
     sha = result.stdout.strip()
@@ -24,11 +32,11 @@ def get_head_sha(script, dest):
     return sha
 
 
-def checkout_ref(script, repo_dir, ref):
+def checkout_ref(script: PipTestEnvironment, repo_dir: str, ref: str) -> None:
     script.run("git", "checkout", ref, cwd=repo_dir)
 
 
-def checkout_new_branch(script, repo_dir, branch):
+def checkout_new_branch(script: PipTestEnvironment, repo_dir: str, branch: str) -> None:
     script.run(
         "git",
         "checkout",
@@ -38,12 +46,12 @@ def checkout_new_branch(script, repo_dir, branch):
     )
 
 
-def do_commit(script, dest):
+def do_commit(script: PipTestEnvironment, dest: str) -> str:
     _git_commit(script, dest, message="test commit", allow_empty=True)
     return get_head_sha(script, dest)
 
 
-def add_commits(script, dest, count):
+def add_commits(script: PipTestEnvironment, dest: str, count: int) -> List[str]:
     """Return a list of the commit hashes from oldest to newest."""
     shas = []
     for _ in range(count):
@@ -53,11 +61,11 @@ def add_commits(script, dest, count):
     return shas
 
 
-def check_rev(repo_dir, rev, expected):
+def check_rev(repo_dir: str, rev: str, expected: Tuple[Optional[str], bool]) -> None:
     assert Git.get_revision_sha(repo_dir, rev) == expected
 
 
-def test_git_dir_ignored(tmpdir):
+def test_git_dir_ignored(tmpdir: Path) -> None:
     """
     Test that a GIT_DIR environment variable is ignored.
     """
@@ -71,7 +79,7 @@ def test_git_dir_ignored(tmpdir):
     assert os.listdir(repo_dir) == [".git"]
 
 
-def test_git_work_tree_ignored(tmpdir):
+def test_git_work_tree_ignored(tmpdir: Path) -> None:
     """
     Test that a GIT_WORK_TREE environment variable is ignored.
     """
@@ -87,12 +95,12 @@ def test_git_work_tree_ignored(tmpdir):
     Git.run_command(["status", repo_dir], extra_environ=env, cwd=repo_dir)
 
 
-def test_get_remote_url(script, tmpdir):
-    source_dir = tmpdir / "source"
-    source_dir.mkdir()
-    source_url = _test_path_to_file_url(source_dir)
+def test_get_remote_url(script: PipTestEnvironment, tmpdir: Path) -> None:
+    source_path = tmpdir / "source"
+    source_path.mkdir()
+    source_url = _test_path_to_file_url(source_path)
 
-    source_dir = str(source_dir)
+    source_dir = str(source_path)
     script.run("git", "init", cwd=source_dir)
     do_commit(script, source_dir)
 
@@ -103,13 +111,13 @@ def test_get_remote_url(script, tmpdir):
     assert remote_url == source_url
 
 
-def test_get_remote_url__no_remote(script, tmpdir):
+def test_get_remote_url__no_remote(script: PipTestEnvironment, tmpdir: Path) -> None:
     """
     Test a repo with no remote.
     """
-    repo_dir = tmpdir / "temp-repo"
-    repo_dir.mkdir()
-    repo_dir = str(repo_dir)
+    repo_path = tmpdir / "temp-repo"
+    repo_path.mkdir()
+    repo_dir = str(repo_path)
 
     script.run("git", "init", cwd=repo_dir)
 
@@ -117,7 +125,7 @@ def test_get_remote_url__no_remote(script, tmpdir):
         Git.get_remote_url(repo_dir)
 
 
-def test_get_current_branch(script):
+def test_get_current_branch(script: PipTestEnvironment) -> None:
     repo_dir = str(script.scratch_path)
 
     script.run("git", "init", cwd=repo_dir)
@@ -135,7 +143,9 @@ def test_get_current_branch(script):
     assert Git.get_current_branch(repo_dir) is None
 
 
-def test_get_current_branch__branch_and_tag_same_name(script, tmpdir):
+def test_get_current_branch__branch_and_tag_same_name(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Check calling get_current_branch() from a branch or tag when the branch
     and tag have the same name.
@@ -154,7 +164,7 @@ def test_get_current_branch__branch_and_tag_same_name(script, tmpdir):
     assert Git.get_current_branch(repo_dir) is None
 
 
-def test_get_revision_sha(script):
+def test_get_revision_sha(script: PipTestEnvironment) -> None:
     repo_dir = str(script.scratch_path)
 
     script.run("git", "init", cwd=repo_dir)
@@ -210,7 +220,7 @@ def test_get_revision_sha(script):
         check_rev(repo_dir, name, (None, False))
 
 
-def test_is_commit_id_equal(script):
+def test_is_commit_id_equal(script: PipTestEnvironment) -> None:
     """
     Test Git.is_commit_id_equal().
     """
@@ -226,7 +236,7 @@ def test_is_commit_id_equal(script):
     assert not Git.is_commit_id_equal(version_pkg_path, None)
 
 
-def test_is_immutable_rev_checkout(script):
+def test_is_immutable_rev_checkout(script: PipTestEnvironment) -> None:
     version_pkg_path = _create_test_package(script)
     commit = script.run("git", "rev-parse", "HEAD", cwd=version_pkg_path).stdout.strip()
     assert Git().is_immutable_rev_checkout(
@@ -238,19 +248,23 @@ def test_is_immutable_rev_checkout(script):
     )
 
 
-def test_get_repository_root(script):
+def test_get_repository_root(script: PipTestEnvironment) -> None:
     version_pkg_path = _create_test_package(script)
     tests_path = version_pkg_path.joinpath("tests")
     tests_path.mkdir()
 
     root1 = Git.get_repository_root(version_pkg_path)
+    assert root1 is not None
     assert os.path.normcase(root1) == os.path.normcase(version_pkg_path)
 
     root2 = Git.get_repository_root(version_pkg_path.joinpath("tests"))
+    assert root2 is not None
     assert os.path.normcase(root2) == os.path.normcase(version_pkg_path)
 
 
-def test_resolve_commit_not_on_branch(script, tmp_path):
+def test_resolve_commit_not_on_branch(
+    script: PipTestEnvironment, tmp_path: pathlib.Path
+) -> None:
     repo_path = tmp_path / "repo"
     repo_file = repo_path / "file.txt"
     clone_path = repo_path / "clone"
@@ -277,10 +291,14 @@ def test_resolve_commit_not_on_branch(script, tmp_path):
 
     # check we can fetch our commit
     rev_options = Git.make_rev_options(commit)
-    Git().fetch_new(str(clone_path), repo_path.as_uri(), rev_options)
+    Git().fetch_new(
+        str(clone_path), HiddenText(repo_path.as_uri(), redacted="*"), rev_options
+    )
 
 
-def _initialize_clonetest_server(repo_path, script, enable_partial_clone):
+def _initialize_clonetest_server(
+    repo_path: pathlib.Path, script: PipTestEnvironment, enable_partial_clone: bool
+) -> pathlib.Path:
     repo_path.mkdir()
     script.run("git", "init", cwd=str(repo_path))
     repo_file = repo_path / "file.txt"
@@ -299,7 +317,7 @@ def _initialize_clonetest_server(repo_path, script, enable_partial_clone):
 
 
 @pytest.mark.skipif(Git().get_git_version() < (2, 17), reason="git too old")
-def test_partial_clone(script, tmp_path):
+def test_partial_clone(script: PipTestEnvironment, tmp_path: pathlib.Path) -> None:
     """Test partial clone w/ a git-server that supports it"""
     repo_path = tmp_path / "repo"
     repo_file = _initialize_clonetest_server(
@@ -311,9 +329,17 @@ def test_partial_clone(script, tmp_path):
     commit = script.run("git", "rev-parse", "HEAD", cwd=str(repo_path)).stdout.strip()
 
     # Check that we can clone at HEAD
-    Git().fetch_new(str(clone_path1), repo_path.as_uri(), Git.make_rev_options())
+    Git().fetch_new(
+        str(clone_path1),
+        HiddenText(repo_path.as_uri(), redacted="*"),
+        Git.make_rev_options(),
+    )
     # Check that we can clone to commit
-    Git().fetch_new(str(clone_path2), repo_path.as_uri(), Git.make_rev_options(commit))
+    Git().fetch_new(
+        str(clone_path2),
+        HiddenText(repo_path.as_uri(), redacted="*"),
+        Git.make_rev_options(commit),
+    )
 
     # Write some additional stuff to git pull
     repo_file.write_text(u"..")
@@ -331,7 +357,9 @@ def test_partial_clone(script, tmp_path):
 
 
 @pytest.mark.skipif(Git().get_git_version() < (2, 17), reason="git too old")
-def test_partial_clone_without_server_support(script, tmp_path):
+def test_partial_clone_without_server_support(
+    script: PipTestEnvironment, tmp_path: pathlib.Path
+) -> None:
     """Test partial clone w/ a git-server that does not support it"""
     repo_path = tmp_path / "repo"
     repo_file = _initialize_clonetest_server(
@@ -343,9 +371,17 @@ def test_partial_clone_without_server_support(script, tmp_path):
     commit = script.run("git", "rev-parse", "HEAD", cwd=str(repo_path)).stdout.strip()
 
     # Check that we can clone at HEAD
-    Git().fetch_new(str(clone_path1), repo_path.as_uri(), Git.make_rev_options())
+    Git().fetch_new(
+        str(clone_path1),
+        HiddenText(repo_path.as_uri(), redacted="*"),
+        Git.make_rev_options(),
+    )
     # Check that we can clone to commit
-    Git().fetch_new(str(clone_path2), repo_path.as_uri(), Git.make_rev_options(commit))
+    Git().fetch_new(
+        str(clone_path2),
+        HiddenText(repo_path.as_uri(), redacted="*"),
+        Git.make_rev_options(commit),
+    )
 
     # Write some additional stuff to git pull
     repo_file.write_text(u"..")
@@ -362,7 +398,9 @@ def test_partial_clone_without_server_support(script, tmp_path):
     )
 
 
-def test_clone_without_partial_clone_support(script, tmp_path):
+def test_clone_without_partial_clone_support(
+    script: PipTestEnvironment, tmp_path: pathlib.Path
+) -> None:
     """Older git clients don't support partial clone. Test the fallback path"""
     repo_path = tmp_path / "repo"
     repo_file = _initialize_clonetest_server(
@@ -372,7 +410,11 @@ def test_clone_without_partial_clone_support(script, tmp_path):
 
     # Check that we can clone w/ old version of git w/o --filter
     with patch("pip._internal.vcs.git.Git.get_git_version", return_value=(2, 16)):
-        Git().fetch_new(str(clone_path), repo_path.as_uri(), Git.make_rev_options())
+        Git().fetch_new(
+            str(clone_path),
+            HiddenText(repo_path.as_uri(), redacted="*"),
+            Git.make_rev_options(),
+        )
 
     repo_file.write_text(u"...")
     script.run("git", "commit", "-am", "third commit", cwd=str(repo_path))
diff --git a/tests/functional/test_vcs_mercurial.py b/tests/functional/test_vcs_mercurial.py
index 841c4d8218e..3ac7ac3d1fc 100644
--- a/tests/functional/test_vcs_mercurial.py
+++ b/tests/functional/test_vcs_mercurial.py
@@ -1,17 +1,19 @@
 import os
 
 from pip._internal.vcs.mercurial import Mercurial
-from tests.lib import _create_test_package, need_mercurial
+from tests.lib import PipTestEnvironment, _create_test_package, need_mercurial
 
 
 @need_mercurial
-def test_get_repository_root(script):
+def test_get_repository_root(script: PipTestEnvironment) -> None:
     version_pkg_path = _create_test_package(script, vcs="hg")
     tests_path = version_pkg_path.joinpath("tests")
     tests_path.mkdir()
 
     root1 = Mercurial.get_repository_root(version_pkg_path)
+    assert root1 is not None
     assert os.path.normcase(root1) == os.path.normcase(version_pkg_path)
 
     root2 = Mercurial.get_repository_root(version_pkg_path.joinpath("tests"))
+    assert root2 is not None
     assert os.path.normcase(root2) == os.path.normcase(version_pkg_path)
diff --git a/tests/functional/test_vcs_subversion.py b/tests/functional/test_vcs_subversion.py
index 4c1d1cb96cf..91627af8688 100644
--- a/tests/functional/test_vcs_subversion.py
+++ b/tests/functional/test_vcs_subversion.py
@@ -2,14 +2,15 @@
 
 from pip._internal.vcs.subversion import Subversion
 from pip._internal.vcs.versioncontrol import RemoteNotFoundError
-from tests.lib import _create_svn_repo, need_svn
+from tests.lib import PipTestEnvironment, _create_svn_repo, need_svn
+from tests.lib.path import Path
 
 
 @need_svn
-def test_get_remote_url__no_remote(script, tmpdir):
-    repo_dir = tmpdir / "temp-repo"
-    repo_dir.mkdir()
-    repo_dir = str(repo_dir)
+def test_get_remote_url__no_remote(script: PipTestEnvironment, tmpdir: Path) -> None:
+    repo_path = tmpdir / "temp-repo"
+    repo_path.mkdir()
+    repo_dir = str(repo_path)
 
     _create_svn_repo(script, repo_dir)
 
@@ -18,12 +19,14 @@ def test_get_remote_url__no_remote(script, tmpdir):
 
 
 @need_svn
-def test_get_remote_url__no_remote_with_setup(script, tmpdir):
-    repo_dir = tmpdir / "temp-repo"
-    repo_dir.mkdir()
-    setup = repo_dir / "setup.py"
+def test_get_remote_url__no_remote_with_setup(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
+    repo_path = tmpdir / "temp-repo"
+    repo_path.mkdir()
+    setup = repo_path / "setup.py"
     setup.touch()
-    repo_dir = str(repo_dir)
+    repo_dir = str(repo_path)
 
     _create_svn_repo(script, repo_dir)
 
diff --git a/tests/functional/test_warning.py b/tests/functional/test_warning.py
index 6e3d23b67f9..a7018944873 100644
--- a/tests/functional/test_warning.py
+++ b/tests/functional/test_warning.py
@@ -3,9 +3,12 @@
 
 import pytest
 
+from tests.lib import PipTestEnvironment
+from tests.lib.path import Path
+
 
 @pytest.fixture
-def warnings_demo(tmpdir):
+def warnings_demo(tmpdir: Path) -> Path:
     demo = tmpdir.joinpath("warnings_demo.py")
     demo.write_text(
         textwrap.dedent(
@@ -23,13 +26,17 @@ def warnings_demo(tmpdir):
     return demo
 
 
-def test_deprecation_warnings_are_correct(script, warnings_demo):
+def test_deprecation_warnings_are_correct(
+    script: PipTestEnvironment, warnings_demo: Path
+) -> None:
     result = script.run("python", warnings_demo, expect_stderr=True)
     expected = "WARNING:pip._internal.deprecations:DEPRECATION: deprecated!\n"
     assert result.stderr == expected
 
 
-def test_deprecation_warnings_can_be_silenced(script, warnings_demo):
+def test_deprecation_warnings_can_be_silenced(
+    script: PipTestEnvironment, warnings_demo: Path
+) -> None:
     script.environ["PYTHONWARNINGS"] = "ignore"
     result = script.run("python", warnings_demo)
     assert result.stderr == ""
@@ -39,19 +46,23 @@ def test_deprecation_warnings_can_be_silenced(script, warnings_demo):
 CPYTHON_DEPRECATION_TEXT = "January 1st, 2020"
 
 
-def test_version_warning_is_not_shown_if_python_version_is_not_2(script):
+def test_version_warning_is_not_shown_if_python_version_is_not_2(
+    script: PipTestEnvironment,
+) -> None:
     result = script.pip("debug", allow_stderr_warning=True)
     assert DEPRECATION_TEXT not in result.stderr, str(result)
     assert CPYTHON_DEPRECATION_TEXT not in result.stderr, str(result)
 
 
-def test_flag_does_nothing_if_python_version_is_not_2(script):
+def test_flag_does_nothing_if_python_version_is_not_2(
+    script: PipTestEnvironment,
+) -> None:
     script.pip("list", "--no-python-version-warning")
 
 
 @pytest.mark.skipif(
     sys.version_info >= (3, 10), reason="distutils is deprecated in 3.10+"
 )
-def test_pip_works_with_warnings_as_errors(script):
+def test_pip_works_with_warnings_as_errors(script: PipTestEnvironment) -> None:
     script.environ["PYTHONWARNINGS"] = "error"
     script.pip("--version")
diff --git a/tests/functional/test_wheel.py b/tests/functional/test_wheel.py
index eec50765a40..dedf22ba8cc 100644
--- a/tests/functional/test_wheel.py
+++ b/tests/functional/test_wheel.py
@@ -7,11 +7,13 @@
 
 from pip._internal.cli.status_codes import ERROR
 from tests.lib import pyversion  # noqa: F401
+from tests.lib import PipTestEnvironment, TestData
+from tests.lib.path import Path
 
 pytestmark = pytest.mark.usefixtures("with_wheel")
 
 
-def add_files_to_dist_directory(folder):
+def add_files_to_dist_directory(folder: Path) -> None:
     (folder / "dist").mkdir(parents=True)
     (folder / "dist" / "a_name-0.0.1.tar.gz").write_text("hello")
     # Not adding a wheel file since that confuses setuptools' backend.
@@ -20,7 +22,9 @@ def add_files_to_dist_directory(folder):
     # )
 
 
-def test_wheel_exit_status_code_when_no_requirements(script):
+def test_wheel_exit_status_code_when_no_requirements(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test wheel exit status code when no requirements specified
     """
@@ -29,7 +33,9 @@ def test_wheel_exit_status_code_when_no_requirements(script):
     assert result.returncode == ERROR
 
 
-def test_wheel_exit_status_code_when_blank_requirements_file(script):
+def test_wheel_exit_status_code_when_blank_requirements_file(
+    script: PipTestEnvironment,
+) -> None:
     """
     Test wheel exit status code when blank requirements file specified
     """
@@ -37,7 +43,7 @@ def test_wheel_exit_status_code_when_blank_requirements_file(script):
     script.pip("wheel", "-r", "blank.txt")
 
 
-def test_pip_wheel_success(script, data):
+def test_pip_wheel_success(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test 'pip wheel' success.
     """
@@ -62,7 +68,7 @@ def test_pip_wheel_success(script, data):
     assert "Successfully built simple" in result.stdout, result.stdout
 
 
-def test_pip_wheel_build_cache(script, data):
+def test_pip_wheel_build_cache(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test 'pip wheel' builds and caches.
     """
@@ -92,7 +98,9 @@ def test_pip_wheel_build_cache(script, data):
     assert "Successfully built simple" not in result.stdout, result.stdout
 
 
-def test_basic_pip_wheel_downloads_wheels(script, data):
+def test_basic_pip_wheel_downloads_wheels(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test 'pip wheel' downloads wheels
     """
@@ -109,7 +117,9 @@ def test_basic_pip_wheel_downloads_wheels(script, data):
     assert "Saved" in result.stdout, result.stdout
 
 
-def test_pip_wheel_build_relative_cachedir(script, data):
+def test_pip_wheel_build_relative_cachedir(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test 'pip wheel' builds and caches with a non-absolute cache directory.
     """
@@ -125,7 +135,9 @@ def test_pip_wheel_build_relative_cachedir(script, data):
     assert result.returncode == 0
 
 
-def test_pip_wheel_builds_when_no_binary_set(script, data):
+def test_pip_wheel_builds_when_no_binary_set(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     data.packages.joinpath("simple-3.0-py2.py3-none-any.whl").touch()
     # Check that the wheel package is ignored
     res = script.pip(
@@ -141,7 +153,9 @@ def test_pip_wheel_builds_when_no_binary_set(script, data):
 
 
 @pytest.mark.skipif("sys.platform == 'win32'")
-def test_pip_wheel_readonly_cache(script, data, tmpdir):
+def test_pip_wheel_readonly_cache(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     cache_dir = tmpdir / "cache"
     cache_dir.mkdir()
     os.chmod(cache_dir, 0o400)  # read-only cache
@@ -160,7 +174,9 @@ def test_pip_wheel_readonly_cache(script, data, tmpdir):
     assert "The cache has been disabled." in str(res), str(res)
 
 
-def test_pip_wheel_builds_editable_deps(script, data):
+def test_pip_wheel_builds_editable_deps(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """
     Test 'pip wheel' finds and builds dependencies of editables
     """
@@ -173,7 +189,7 @@ def test_pip_wheel_builds_editable_deps(script, data):
     result.did_create(wheel_file_path)
 
 
-def test_pip_wheel_builds_editable(script, data):
+def test_pip_wheel_builds_editable(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test 'pip wheel' builds an editable package
     """
@@ -187,7 +203,9 @@ def test_pip_wheel_builds_editable(script, data):
 
 
 @pytest.mark.network
-def test_pip_wheel_git_editable_keeps_clone(script, tmpdir):
+def test_pip_wheel_git_editable_keeps_clone(
+    script: PipTestEnvironment, tmpdir: Path
+) -> None:
     """
     Test that `pip wheel -e giturl` preserves a git clone in src.
     """
@@ -205,7 +223,9 @@ def test_pip_wheel_git_editable_keeps_clone(script, tmpdir):
     assert (tmpdir / "src" / "pip-test-package" / ".git").exists()
 
 
-def test_pip_wheel_builds_editable_does_not_create_zip(script, data, tmpdir):
+def test_pip_wheel_builds_editable_does_not_create_zip(
+    script: PipTestEnvironment, data: TestData, tmpdir: Path
+) -> None:
     """
     Test 'pip wheel' of editables does not create zip files
     (regression test for issue #9122)
@@ -219,7 +239,7 @@ def test_pip_wheel_builds_editable_does_not_create_zip(script, data, tmpdir):
     assert wheels[0].endswith(".whl")
 
 
-def test_pip_wheel_fail(script, data):
+def test_pip_wheel_fail(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test 'pip wheel' failure.
     """
@@ -239,7 +259,7 @@ def test_pip_wheel_fail(script, data):
     assert result.returncode != 0
 
 
-def test_pip_wheel_source_deps(script, data):
+def test_pip_wheel_source_deps(script: PipTestEnvironment, data: TestData) -> None:
     """
     Test 'pip wheel' finds and builds source archive dependencies
     of wheels
@@ -258,7 +278,9 @@ def test_pip_wheel_source_deps(script, data):
     assert "Successfully built source" in result.stdout, result.stdout
 
 
-def test_wheel_package_with_latin1_setup(script, data):
+def test_wheel_package_with_latin1_setup(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Create a wheel from a package with latin-1 encoded setup.py."""
 
     pkg_to_wheel = data.packages.joinpath("SetupPyLatin1")
@@ -266,7 +288,9 @@ def test_wheel_package_with_latin1_setup(script, data):
     assert "Successfully built SetupPyUTF8" in result.stdout
 
 
-def test_pip_wheel_with_pep518_build_reqs(script, data, common_wheels):
+def test_pip_wheel_with_pep518_build_reqs(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     result = script.pip(
         "wheel",
         "--no-index",
@@ -283,7 +307,9 @@ def test_pip_wheel_with_pep518_build_reqs(script, data, common_wheels):
     assert "Installing build dependencies" in result.stdout, result.stdout
 
 
-def test_pip_wheel_with_pep518_build_reqs_no_isolation(script, data):
+def test_pip_wheel_with_pep518_build_reqs_no_isolation(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     script.pip_install_local("simplewheel==2.0")
     result = script.pip(
         "wheel",
@@ -300,7 +326,9 @@ def test_pip_wheel_with_pep518_build_reqs_no_isolation(script, data):
     assert "Installing build dependencies" not in result.stdout, result.stdout
 
 
-def test_pip_wheel_with_user_set_in_config(script, data, common_wheels):
+def test_pip_wheel_with_user_set_in_config(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     config_file = script.scratch_path / "pip.conf"
     script.environ["PIP_CONFIG_FILE"] = str(config_file)
     config_file.write_text("[install]\nuser = true")
@@ -314,7 +342,9 @@ def test_pip_wheel_with_user_set_in_config(script, data, common_wheels):
     sys.platform.startswith("win"),
     reason="The empty extension module does not work on Win",
 )
-def test_pip_wheel_ext_module_with_tmpdir_inside(script, data, common_wheels):
+def test_pip_wheel_ext_module_with_tmpdir_inside(
+    script: PipTestEnvironment, data: TestData, common_wheels: Path
+) -> None:
     tmpdir = data.src / "extension/tmp"
     tmpdir.mkdir()
     script.environ["TMPDIR"] = str(tmpdir)
@@ -330,7 +360,9 @@ def test_pip_wheel_ext_module_with_tmpdir_inside(script, data, common_wheels):
 
 
 @pytest.mark.network
-def test_pep517_wheels_are_not_confused_with_other_files(script, data):
+def test_pep517_wheels_are_not_confused_with_other_files(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Check correct wheels are copied. (#6196)"""
     pkg_to_wheel = data.src / "withpyproject"
     add_files_to_dist_directory(pkg_to_wheel)
@@ -343,7 +375,9 @@ def test_pep517_wheels_are_not_confused_with_other_files(script, data):
     result.did_create(wheel_file_path)
 
 
-def test_legacy_wheels_are_not_confused_with_other_files(script, data):
+def test_legacy_wheels_are_not_confused_with_other_files(
+    script: PipTestEnvironment, data: TestData
+) -> None:
     """Check correct wheels are copied. (#6196)"""
     pkg_to_wheel = data.src / "simplewheel-1.0"
     add_files_to_dist_directory(pkg_to_wheel)
diff --git a/tests/lib/__init__.py b/tests/lib/__init__.py
index dde1f3d6939..eafc53de564 100644
--- a/tests/lib/__init__.py
+++ b/tests/lib/__init__.py
@@ -1,5 +1,6 @@
 import json
 import os
+import pathlib
 import re
 import shutil
 import site
@@ -11,7 +12,18 @@
 from hashlib import sha256
 from io import BytesIO
 from textwrap import dedent
-from typing import Any, Callable, Dict, Iterator, List, Optional, Tuple, Union, cast
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Callable,
+    Dict,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+    Union,
+    cast,
+)
 from zipfile import ZipFile
 
 import pytest
@@ -30,6 +42,14 @@
 from tests.lib.venv import VirtualEnvironment
 from tests.lib.wheel import make_wheel
 
+if TYPE_CHECKING:
+    # Literal was introduced in Python 3.8.
+    from typing import Literal
+
+    ResolverVariant = Literal["resolvelib", "legacy"]
+else:
+    ResolverVariant = str
+
 DATA_DIR = Path(__file__).parent.parent.joinpath("data").resolve()
 SRC_DIR = Path(__file__).resolve().parent.parent.parent
 
@@ -266,11 +286,11 @@ def assert_installed(
         self,
         pkg_name: str,
         editable: bool = True,
-        with_files: Optional[List[Path]] = None,
-        without_files: Optional[List[Path]] = None,
+        with_files: Optional[List[str]] = None,
+        without_files: Optional[List[str]] = None,
         without_egg_link: bool = False,
         use_user_site: bool = False,
-        sub_dir: bool = False,
+        sub_dir: Optional[str] = None,
     ) -> None:
         with_files = with_files or []
         without_files = without_files or []
@@ -358,16 +378,16 @@ def assert_installed(
                     f"Package directory {pkg_dir!r} has unexpected content {f}"
                 )
 
-    def did_create(self, path: Path, message: Optional[str] = None) -> None:
+    def did_create(self, path: str, message: Optional[str] = None) -> None:
         assert str(path) in self.files_created, _one_or_both(message, self)
 
-    def did_not_create(self, path: Path, message: Optional[str] = None) -> None:
+    def did_not_create(self, path: str, message: Optional[str] = None) -> None:
         assert str(path) not in self.files_created, _one_or_both(message, self)
 
-    def did_update(self, path: Path, message: Optional[str] = None) -> None:
+    def did_update(self, path: str, message: Optional[str] = None) -> None:
         assert str(path) in self.files_updated, _one_or_both(message, self)
 
-    def did_not_update(self, path: Path, message: Optional[str] = None) -> None:
+    def did_not_update(self, path: str, message: Optional[str] = None) -> None:
         assert str(path) not in self.files_updated, _one_or_both(message, self)
 
 
@@ -567,7 +587,7 @@ def _find_traverse(self, path: str, result: Dict[str, FoundDir]) -> None:
     def run(
         self,
         *args: str,
-        cwd: Optional[str] = None,
+        cwd: Union[None, str, pathlib.Path] = None,
         allow_stderr_error: Optional[bool] = None,
         allow_stderr_warning: Optional[bool] = None,
         allow_error: bool = False,
@@ -847,8 +867,8 @@ def _git_commit(
 
 
 def _vcs_add(
-    script: PipTestEnvironment, version_pkg_path: str, vcs: str = "git"
-) -> str:
+    script: PipTestEnvironment, version_pkg_path: Path, vcs: str = "git"
+) -> Path:
     if vcs == "git":
         script.run("git", "init", cwd=version_pkg_path)
         script.run("git", "add", ".", cwd=version_pkg_path)
@@ -874,7 +894,7 @@ def _vcs_add(
         checkout_path: str = script.scratch_path / "pip-test-package"
 
         # svn internally stores windows drives as uppercase; we'll match that.
-        checkout_path = checkout_path.replace("c:", "C:")
+        checkout_path = Path(checkout_path.replace("c:", "C:"))
 
         version_pkg_path = checkout_path
     elif vcs == "bazaar":
@@ -949,7 +969,7 @@ def _create_test_package_with_subdirectory(
 
 def _create_test_package_with_srcdir(
     script: PipTestEnvironment, name: str = "version_pkg", vcs: str = "git"
-) -> str:
+) -> Path:
     script.scratch_path.joinpath(name).mkdir()
     version_pkg_path = script.scratch_path / name
     subdir_path = version_pkg_path.joinpath("subdir")
@@ -979,7 +999,7 @@ def _create_test_package_with_srcdir(
 
 def _create_test_package(
     script: PipTestEnvironment, name: str = "version_pkg", vcs: str = "git"
-) -> str:
+) -> Path:
     script.scratch_path.joinpath(name).mkdir()
     version_pkg_path = script.scratch_path / name
     _create_main_file(version_pkg_path, name=name, output="0.1")
@@ -1101,9 +1121,9 @@ def create_basic_wheel_for_package(
     name: str,
     version: str,
     depends: Optional[List[str]] = None,
-    extras: Dict[str, str] = None,
+    extras: Dict[str, List[str]] = None,
     requires_python: Optional[str] = None,
-    extra_files: Optional[Dict[str, str]] = None,
+    extra_files: Optional[Dict[str, Union[bytes, str]]] = None,
 ) -> Path:
     if depends is None:
         depends = []
diff --git a/tests/lib/git_submodule_helpers.py b/tests/lib/git_submodule_helpers.py
index 80afd9474a0..32a3c000287 100644
--- a/tests/lib/git_submodule_helpers.py
+++ b/tests/lib/git_submodule_helpers.py
@@ -26,7 +26,7 @@ def _change_test_package_submodule(
 
 
 def _pull_in_submodule_changes_to_module(
-    env: PipTestEnvironment, module_path: Path, rel_path: Path
+    env: PipTestEnvironment, module_path: Path, rel_path: str
 ) -> None:
     """
     Args:
@@ -39,7 +39,7 @@ def _pull_in_submodule_changes_to_module(
 
 
 def _create_test_package_with_submodule(
-    env: PipTestEnvironment, rel_path: Path
+    env: PipTestEnvironment, rel_path: str
 ) -> Tuple[Path, Path]:
     """
     Args:
diff --git a/tests/lib/wheel.py b/tests/lib/wheel.py
index aa4086941ba..878364cf792 100644
--- a/tests/lib/wheel.py
+++ b/tests/lib/wheel.py
@@ -48,7 +48,7 @@ class Default(Enum):
 Defaulted = Union[Default, T]
 
 
-def ensure_binary(value: AnyStr) -> bytes:
+def ensure_binary(value: Union[bytes, str]) -> bytes:
     if isinstance(value, bytes):
         return value
     return value.encode()
@@ -163,7 +163,7 @@ def make_entry_points_file(
     )
 
 
-def make_files(files: Dict[str, AnyStr]) -> List[File]:
+def make_files(files: Dict[str, Union[bytes, str]]) -> List[File]:
     return [File(name, ensure_binary(contents)) for name, contents in files.items()]
 
 
@@ -295,7 +295,7 @@ def make_wheel(
     metadata: Defaulted[Optional[AnyStr]] = _default,
     metadata_body: Defaulted[AnyStr] = _default,
     metadata_updates: Defaulted[Dict[str, HeaderValue]] = _default,
-    extra_files: Defaulted[Dict[str, AnyStr]] = _default,
+    extra_files: Defaulted[Dict[str, Union[bytes, str]]] = _default,
     extra_metadata_files: Defaulted[Dict[str, AnyStr]] = _default,
     extra_data_files: Defaulted[Dict[str, AnyStr]] = _default,
     console_scripts: Defaulted[List[str]] = _default,