Shared tests with hypothesis throws an Event loop is closed error

[gryevns]

When you have a class containing some shared tests (e.g. for contract testing between several implementations of an interface), and use both hypothesis and pytest-asyncio on the shared tests, pytest will raise an error when running the test for the second time.

HypothesisWorks/hypothesis#3122

Example

import hypothesis
import hypothesis.strategies
import pytest

class Shared:
    @pytest.mark.asyncio
    @hypothesis.given(value=hypothesis.strategies.integers())
    async def test_foo(self, value: int) -> None:
        assert value == value

class TestCaseOne(Shared):
    pass

class TestCaseTwo(Shared):
    pass

================================= test session starts ==================================
platform darwin -- Python 3.9.4, pytest-6.2.5, py-1.10.0, pluggy-1.0.0
rootdir: /Users/garyevans/Projects/pytest-async-hypothesis
plugins: asyncio-0.16.0, hypothesis-6.23.3
collected 2 items                                                                      

test.py .F                                                                       [100%]

======================================= FAILURES =======================================
_________________________________ TestCaseTwo.test_foo _________________________________

self = <test.TestCaseTwo object at 0x1069abe20>

    @pytest.mark.asyncio
>   @hypothesis.given(value=hypothesis.strategies.integers())

test.py:8: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../Library/Caches/pypoetry/virtualenvs/pytest-async-hypothesis-BRvTXcHz-py3.9/lib/python3.9/site-packages/pytest_asyncio/plugin.py:191: in inner
    coro = func(**kwargs)
../../Library/Caches/pypoetry/virtualenvs/pytest-async-hypothesis-BRvTXcHz-py3.9/lib/python3.9/site-packages/pytest_asyncio/plugin.py:193: in inner
    task = asyncio.ensure_future(coro, loop=_loop)
../../.pyenv/versions/3.9.4/lib/python3.9/asyncio/tasks.py:667: in ensure_future
    task = loop.create_task(coro_or_future)
../../.pyenv/versions/3.9.4/lib/python3.9/asyncio/base_events.py:431: in create_task
    self._check_closed()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <_UnixSelectorEventLoop running=False closed=True debug=False>

    def _check_closed(self):
        if self._closed:
>           raise RuntimeError('Event loop is closed')
E           RuntimeError: Event loop is closed

../../.pyenv/versions/3.9.4/lib/python3.9/asyncio/base_events.py:510: RuntimeError
-------------------------------------- Hypothesis --------------------------------------
Falsifying example: test_foo(
    value=0, self=<test.TestCaseTwo at 0x1069abe20>,
)
=============================== short test summary info ================================
FAILED test.py::TestCaseTwo::test_foo - RuntimeError: Event loop is closed
============================= 1 failed, 1 passed in 0.13s ==============================
sys:1: RuntimeWarning: coroutine 'Shared.test_foo' was never awaited

Environment

Package          Version
---------------- -------
hypothesis       6.23.3
pytest           6.2.5
pytest-asyncio   0.16.0

Workaround

If we modify the event_loop fixture and do not close the loop by default then the tests pass as expected.

pytest-asyncio/tests/test_hypothesis_integration.py

Lines 11 to 15 in f21e0da

	@pytest.fixture(scope="module")
	def event_loop():
	loop = asyncio.get_event_loop_policy().new_event_loop()
	yield loop
	loop.close()

[simon-liebehenschel]

A workaround by gryevns did not help me.

I've tried to wrap all my fixtures with the with contextlib.suppress(RuntimeError): to at least temporary hide the error, but I still get an exception:

def finalizer():
        """Yield again, to finalize."""
    
        async def async_finalizer():
            try:
                await gen_obj.__anext__()
            except StopAsyncIteration:
                pass
            else:
                msg = "Async generator fixture didn't stop."
                msg += "Yield only once."
                raise ValueError(msg)
    
>       loop.run_until_complete(async_finalizer())

../venv/lib/python3.9/site-packages/pytest_asyncio/plugin.py:139: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python3.9/asyncio/base_events.py:617: in run_until_complete
    self._check_closed()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <_UnixSelectorEventLoop running=False closed=True debug=True>

    def _check_closed(self):
        if self._closed:
>           raise RuntimeError('Event loop is closed')
E           RuntimeError: Event loop is closed

/usr/lib/python3.9/asyncio/base_events.py:510: RuntimeError