Pytest is used to run tests.
Do not add @pytest.mark.asyncio to any test. Async tests are automatically detected and run by the async runner; the decorator is unnecessary clutter.
Do not add a -> None return type annotation to test functions. This is not a common convention in pytest and adds unnecessary verbosity.
When mocking a class, do not define a new class. Use unittest.mock.MagicMock or unittest.mock.AsyncMock, with the spec constructor argument when necessary.
The name of the mocked class should be prefixed with mock, not fake.
Prefer pytest fixtures over helper methods.
Do not repeat fixtures, if a fixture is needed in multiple test files, place it in a conftest.py file.
When creating a fixture follow this pattern:
```
@pytest.fixture(name="<fixture_name>"[, scope="<scope>"])
def <fixture_name>_fixture() -> <return_type>:
    ...
```
Only specify the scope argument when the value is something other than "function".
Prefer pytest.mark.parametrize over creating individual tests for different input types.
If a fixture is needed for a test, but either does not return a value or the value is not used in the test, use the @pytest.mark.usefixtures decorator.
tests/conftest.py contains a restore_environ_fixture fixture that restores the environment variables to their original state after each test, it is defined with autouse=True so it is automatically applied to all tests. If you need to modify the environment variables in a test, do so using os.environ and the fixture will restore them after the test completes. There is no need to use monkeypatch.setenv to modify environment variables in tests.
Avoid defensive programming in tests. If a test fails, it should fail loudly and clearly, rather than silently passing due to defensive checks. For example
```
data = results["data"]
```
is preferred over
```
data = results.get("data")
```
Simply allow the resulting KeyError to be raised if the "data" key is not present in the results dictionary, as this will provide a clear indication of what went wrong in the test.

Common Commands

# Focused test loop
uv run pytest -k "<pattern>"

# Run all tests
uv run pytest

Do Not Write Tests For

Documentation.
Test helper code under tests/_utils/.
Package metadata or wheel installation behavior.

References

pyproject.toml
tests/conftest.py

python-tests

Python Test Style