Remove imported third-party packages so that the auto-cov functionali…

…ty will happen early and not affect test coverage on those packages. Fixes #2.

CHANGES.rst

@@ -1,3 +1,9 @@
+v4.0.1
+======
+
+#2: In enabler, remove third-party packages from sys.modules
+to avoid spurious non-coverage of lines covered at import time.
+
 v4.0.0
 ======
 

jaraco/test/pytest/enabler.py

@@ -1,6 +1,7 @@
 import contextlib
 import shlex
 import types
+import sys
 
 import toml
 from jaraco.context import suppress
@@ -35,6 +36,20 @@ def pytest_load_initial_conftests(early_config, parser, args):
     _pytest_cov_check(plugins, early_config, parser, args)
 
 
+def _remove_deps():
+    """
+    Coverage will not detect function definitions as being covered
+    if the functions are defined before coverage is invoked. As
+    a result, when testing any of the dependencies above, their
+    functions will appear not to be covered. To avoid this behavior,
+    unload the modules above so they may be tested for coverage
+    on import as well.
+    """
+    del sys.modules['jaraco.functools']
+    del sys.modules['jaraco.context']
+    del sys.modules['toml']
+
+
 def _pytest_cov_check(plugins, early_config, parser, args):  # pragma: nocover
     """
     pytest_cov runs its command-line checks so early that no hooks
@@ -50,6 +65,7 @@ def _pytest_cov_check(plugins, early_config, parser, args):  # pragma: nocover
     )
     if not new_args or not plugin_enabled:
         return
+    _remove_deps()
     parser.parse_known_and_unknown_args(new_args, early_config.known_args_namespace)
     with contextlib.suppress(ImportError):
         import pytest_cov.plugin