mypy-pytest-parametrize
Check pytest.mark.parametrize values against test annotations.
For example, this plugin reports the float passed to a parameter annotated as int:
"""Showcase errors in pytest parametrized values."""
import pytest
@pytest.mark.parametrize(
argnames="arg",
argvalues=[
123,
456.789, # type: ignore[pytest-parametrize]
],
)
def test_foo(arg: int) -> None:
"""Check a parametrized integer."""
assert arg > 0Why?
pytest accepts parametrized values without checking them against the test’s annotations. This plugin lets mypy find incompatible values before the tests run. It supports multiple parameters, stacked decorators, and inline pytest.param calls.
Installation
pip install "git+https://github.com/adamtheturtle/mypy-pytest-parametrize.git"This is tested on Python 3.11+ with mypy 2.4 and pytest 9.1+. The package has not yet been published to PyPI.
Configure mypy to use the plugin
Add the plugin to your mypy configuration file:
pyproject.toml:
[tool.mypy]
plugins = [
"mypy_pytest_parametrize",
]mypy.ini, .mypy.ini, or setup.cfg:
[mypy]
plugins = mypy_pytest_parametrizeIndirect fixtures and static limits
indirect=True is excluded because its values are fixture inputs, rather than the values received by the test. With indirect=["fixture_name"], the other parameters are still checked.
Parameter names and fixture routing determined at runtime are not checked. Stored decorator objects and class-level parametrization are also excluded. Stored pytest.param objects and starred values within a row are also skipped when their individual types are unavailable. Values typed as Any retain mypy’s usual behavior.
The plugin follows the proposal in pytest issue #9334.
1 maintainer
Metadata
1 maintainer
Release files for mypy-pytest-parametrize 2026.10.5
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