pytest-dev / pytest-dev/pytest-asyncio
`pytest_asyncio_loop_factories` hook is not called when `pytest.mark.asyncio` is added via parametrization
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Description
Description
If pytest.mark.asyncio is added via parametrization (pytest.mark.parametrize() or pytest.fixture(params=...)), the test functions ignores the configured loop factories.
Steps to reproduce
In conftest.py:
from typing import Any
import uvloop
def pytest_asyncio_loop_factories() -> dict[str, Any]:
return {"uvloop": uvloop.new_event_loop}
In test_async.py:
import asyncio
import uvloop
import pytest
import trio
@pytest.mark.parametrize(
"backend",
[
pytest.param("asyncio", marks=pytest.mark.asyncio),
pytest.param("trio", marks=pytest.mark.trio), # <- Come from pytest-trio
]
)
async def test_async(backend: str) -> None:
match backend:
case "asyncio":
assert isinstance(asyncio.get_running_loop(), uvloop.Loop)
case "trio":
assert trio.lowlevel.current_root_task() is not None
Expected the runner to be uvloop.Loop but it uses the default loop.
Workaround
There is a workaround possible to avoid the issue by using the test inheritance:
import asyncio
import uvloop
import pytest
import trio
class _BaseTestAsync:
async def test_async(self, backend: str) -> None:
match backend:
case "asyncio":
assert isinstance(asyncio.get_running_loop(), uvloop.Loop)
case "trio":
assert trio.lowlevel.current_root_task() is not None
@pytest.mark.asyncio
class TestAsyncIO(_BaseTestAsync):
@pytest.fixture
@staticmethod
def backend() -> str:
return "asyncio"
@pytest.mark.trio
class TestTrio(_BaseTestAsync):
@pytest.fixture
@staticmethod
def backend() -> str:
return "trio"
But compared to fixture parametrization, it is a bit complicated.
Use case
I have a project which must run with asyncio and trio but do not rely on anyio, therefore I use the fixture parametrization to test on all supported runners.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the issue using the conftest.py and test_async.py examples, then trace pytest-asyncio's handling of parametrized asyncio marks and loop-factory configuration. Done means parametrized tests marked with pytest.mark.asyncio use the configured uvloop factory while other parametrized runners continue to work.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- testing-qa
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100