diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f6eac70ca..d5fa75b7a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -11,11 +11,11 @@ on:
     - cron: "0 0 * * *"
 
 jobs:
-  python-coverage:
+  python-exhaustive:
     uses: ./.github/workflows/.nox-session.yml
     with:
       job-name: "python-{0}"
-      session-name: test_python_suite
+      session-name: test_python
       session-arguments: --maxfail=3
   python-environments:
     uses: ./.github/workflows/.nox-session.yml
diff --git a/noxfile.py b/noxfile.py
index ac9fcf08f..a50ba1912 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -200,7 +200,7 @@ def test_python_types(session: Session) -> None:
     install_requirements_file(session, "check-types")
     install_requirements_file(session, "pkg-deps")
     install_requirements_file(session, "pkg-extras")
-    session.run("mypy", "--strict", "src/idom")
+    session.run("mypy", "--show-error-codes", "--strict", "src/idom")
 
 
 @nox.session
diff --git a/src/idom/_option.py b/src/idom/_option.py
index e0a303ac9..1367e6bd9 100644
--- a/src/idom/_option.py
+++ b/src/idom/_option.py
@@ -103,7 +103,7 @@ def __init__(self, new_opt: Option[_O], name: str) -> None:
         self._new_opt = new_opt
 
     @property  # type: ignore
-    def _current(self) -> _O:  # type: ignore
+    def _current(self) -> _O:
         warnings.warn(
             f"{self.name!r} has been renamed to {self._new_opt.name!r}",
             DeprecationWarning,
diff --git a/src/idom/core/component.py b/src/idom/core/component.py
index 5ef0f1844..0bf62c9a7 100644
--- a/src/idom/core/component.py
+++ b/src/idom/core/component.py
@@ -2,13 +2,13 @@
 
 import inspect
 from functools import wraps
-from typing import Any, Callable, Dict, Optional, Tuple, Union
+from typing import Any, Callable, Dict, Optional, Tuple
 
 from .types import ComponentType, VdomDict
 
 
 def component(
-    function: Callable[..., Union[ComponentType, VdomDict | None]]
+    function: Callable[..., ComponentType | VdomDict | str | None]
 ) -> Callable[..., Component]:
     """A decorator for defining a new component.
 
@@ -39,7 +39,7 @@ class Component:
 
     def __init__(
         self,
-        function: Callable[..., ComponentType | VdomDict | None],
+        function: Callable[..., ComponentType | VdomDict | str | None],
         key: Optional[Any],
         args: Tuple[Any, ...],
         kwargs: Dict[str, Any],
@@ -51,7 +51,7 @@ def __init__(
         self._kwargs = kwargs
         self._sig = sig
 
-    def render(self) -> VdomDict | ComponentType | None:
+    def render(self) -> ComponentType | VdomDict | str | None:
         return self.type(*self._args, **self._kwargs)
 
     def should_render(self, new: Component) -> bool:
diff --git a/src/idom/core/hooks.py b/src/idom/core/hooks.py
index 45e7c7dd9..428f9a963 100644
--- a/src/idom/core/hooks.py
+++ b/src/idom/core/hooks.py
@@ -23,7 +23,6 @@
 
 from typing_extensions import Protocol
 
-from idom.config import IDOM_DEBUG_MODE
 from idom.utils import Ref
 
 from ._thread_local import ThreadLocal
@@ -226,9 +225,6 @@ def use_debug_value(
             :func:`id` is different). By default these are inferred based on local
             variables that are referenced by the given function.
     """
-    if not IDOM_DEBUG_MODE.current:
-        return  # pragma: no cover
-
     old: Ref[Any] = _use_const(lambda: Ref(object()))
     memo_func = message if callable(message) else lambda: message
     new = use_memo(memo_func, dependencies)
@@ -541,7 +537,7 @@ def _try_to_infer_closure_values(
         else:
             return None
     else:
-        return cast("Sequence[Any] | None", values)
+        return values
 
 
 def current_hook() -> LifeCycleHook:
diff --git a/src/idom/core/layout.py b/src/idom/core/layout.py
index a7d21b87c..db861142d 100644
--- a/src/idom/core/layout.py
+++ b/src/idom/core/layout.py
@@ -234,7 +234,7 @@ def _render_component(
             old_parent_model = parent.model.current
             old_parent_children = old_parent_model["children"]
             parent.model.current = {
-                **old_parent_model,
+                **old_parent_model,  # type: ignore[misc]
                 "children": [
                     *old_parent_children[:index],
                     new_state.model.current,
diff --git a/src/idom/core/types.py b/src/idom/core/types.py
index 3943a154b..a2b7cc902 100644
--- a/src/idom/core/types.py
+++ b/src/idom/core/types.py
@@ -44,7 +44,7 @@ class ComponentType(Protocol):
     This is used to see if two component instances share the same definition.
     """
 
-    def render(self) -> VdomDict | ComponentType | None:
+    def render(self) -> VdomDict | ComponentType | str | None:
         """Render the component's view model."""
 
     def should_render(self: _OwnType, new: _OwnType) -> bool:
diff --git a/src/idom/testing/display.py b/src/idom/testing/display.py
index 4a7608d32..5e315111e 100644
--- a/src/idom/testing/display.py
+++ b/src/idom/testing/display.py
@@ -12,7 +12,6 @@
     async_playwright,
 )
 
-from idom import html
 from idom.config import IDOM_TESTING_DEFAULT_TIMEOUT
 from idom.types import RootComponentConstructor
 
@@ -49,7 +48,7 @@ async def goto(self, path: str, query: Any | None = None) -> None:
         await self.page.goto(self.backend.url(path, query))
 
     async def root_element(self) -> ElementHandle:
-        element = await self.page.wait_for_selector(f"#app", state="attached")
+        element = await self.page.wait_for_selector("#app", state="attached")
         if element is None:
             raise RuntimeError("Root element not attached")  # pragma: no cover
         return element
diff --git a/src/idom/utils.py b/src/idom/utils.py
index ec114b2c3..e176da660 100644
--- a/src/idom/utils.py
+++ b/src/idom/utils.py
@@ -56,7 +56,9 @@ def __repr__(self) -> str:
         return f"{type(self).__name__}({current})"
 
 
-def html_to_vdom(html: str, *transforms: _ModelTransform, strict: bool = True) -> VdomDict:
+def html_to_vdom(
+    html: str, *transforms: _ModelTransform, strict: bool = True
+) -> VdomDict:
     """Transform HTML into a DOM model. Unique keys can be provided to HTML elements
     using a ``key=...`` attribute within your HTML tag.
 
@@ -82,7 +84,9 @@ def html_to_vdom(html: str, *transforms: _ModelTransform, strict: bool = True) -
         recover=not strict,
     )
     try:
-        nodes: List = fragments_fromstring(html, no_leading_text=True, parser=parser)
+        nodes: list[etree._Element] = fragments_fromstring(
+            html, no_leading_text=True, parser=parser
+        )
     except etree.XMLSyntaxError as e:
         if not strict:
             raise e  # pragma: no cover
@@ -139,10 +143,11 @@ def _etree_to_vdom(
     attributes = dict(node.items())
     key = attributes.pop("key", None)
 
+    vdom: VdomDict
     if hasattr(idom.html, node.tag):
         vdom = getattr(idom.html, node.tag)(attributes, *children, key=key)
     else:
-        vdom: VdomDict = {"tagName": node.tag}
+        vdom = {"tagName": node.tag}
         if children:
             vdom["children"] = children
         if attributes:
@@ -160,7 +165,7 @@ def _etree_to_vdom(
     return vdom
 
 
-def _mutate_vdom(vdom: VdomDict):
+def _mutate_vdom(vdom: VdomDict) -> None:
     """Performs any necessary mutations on the VDOM attributes to meet VDOM spec.
 
     Currently, this function only transforms the ``style`` attribute into a dictionary whose keys are
@@ -216,5 +221,5 @@ def _hypen_to_camel_case(string: str) -> str:
     return first.lower() + remainder.title().replace("-", "")
 
 
-class HTMLParseError(etree.LxmlSyntaxError):
+class HTMLParseError(etree.LxmlSyntaxError):  # type: ignore[misc]
     """Raised when an HTML document cannot be parsed using strict parsing."""
diff --git a/tests/test_core/test_layout.py b/tests/test_core/test_layout.py
index 60d39e65e..42c9d00c3 100644
--- a/tests/test_core/test_layout.py
+++ b/tests/test_core/test_layout.py
@@ -20,7 +20,7 @@
     capture_idom_logs,
 )
 from idom.utils import Ref
-from tests.tooling.asserts import assert_same_items
+from tests.tooling.hooks import use_toggle
 
 
 @pytest.fixture(autouse=True)
@@ -495,11 +495,6 @@ def SomeComponent():
     )
 
 
-def use_toggle(init=False):
-    state, set_state = idom.hooks.use_state(init)
-    return state, lambda: set_state(lambda old: not old)
-
-
 async def test_model_key_preserves_callback_identity_for_common_elements(caplog):
     called_good_trigger = idom.Ref(False)
     good_handler = StaticEventHandler()
@@ -818,13 +813,9 @@ async def test_elements_and_components_with_the_same_key_can_be_interchanged():
     set_toggle = idom.Ref()
     effects = []
 
-    def use_toggle():
-        state, set_state = idom.hooks.use_state(True)
-        return state, lambda: set_state(not state)
-
     @idom.component
     def Root():
-        toggle, set_toggle.current = use_toggle()
+        toggle, set_toggle.current = use_toggle(True)
         if toggle:
             return SomeComponent("x")
         else:
diff --git a/tests/test_html.py b/tests/test_html.py
index d4fe685d8..269e9e5a7 100644
--- a/tests/test_html.py
+++ b/tests/test_html.py
@@ -1,18 +1,9 @@
 import pytest
 
-from idom import component, config, html, use_state
+from idom import component, config, html
 from idom.testing import DisplayFixture, poll
 from idom.utils import Ref
-
-
-def use_toggle(initial=True):
-    state, set_state = use_state(initial)
-    return state, lambda: set_state(not state)
-
-
-def use_counter(initial_value):
-    state, set_state = use_state(initial_value)
-    return state, lambda: set_state(state + 1)
+from tests.tooling.hooks import use_counter, use_toggle
 
 
 async def test_script_mount_unmount(display: DisplayFixture):
@@ -20,7 +11,7 @@ async def test_script_mount_unmount(display: DisplayFixture):
 
     @component
     def Root():
-        is_mounted, toggle_is_mounted.current = use_toggle()
+        is_mounted, toggle_is_mounted.current = use_toggle(True)
         return html.div(
             html.div({"id": "mount-state", "data-value": False}),
             HasScript() if is_mounted else html.div(),
diff --git a/tests/tooling/hooks.py b/tests/tooling/hooks.py
new file mode 100644
index 000000000..f6488af8a
--- /dev/null
+++ b/tests/tooling/hooks.py
@@ -0,0 +1,11 @@
+from idom import use_state
+
+
+def use_toggle(init=False):
+    state, set_state = use_state(init)
+    return state, lambda: set_state(lambda old: not old)
+
+
+def use_counter(initial_value):
+    state, set_state = use_state(initial_value)
+    return state, lambda: set_state(state + 1)