Limit event_loop_policy parametrization to async tests

changelog.d/796.fixed.rst

@@ -0,0 +1 @@
+Parametrized ``event_loop_policy`` fixtures no longer parametrize synchronous tests.

pytest_asyncio/plugin.py

@@ -730,6 +730,7 @@ def pytest_generate_tests(metafunc: pytest.Metafunc) -> None:
         metafunc.definition
     )
     if specialized_item_class is None:
+        _remove_autouse_event_loop_policy_for_sync_tests(metafunc)
         return
 
     asyncio_marker = _resolve_asyncio_marker(metafunc.definition)
@@ -788,6 +789,25 @@ def pytest_generate_tests(metafunc: pytest.Metafunc) -> None:
     )
 
 
+def _remove_autouse_event_loop_policy_for_sync_tests(
+    metafunc: pytest.Metafunc,
+) -> None:
+    fixture_name = event_loop_policy.__name__
+    fixtureinfo = metafunc.definition._fixtureinfo
+    if fixture_name in fixtureinfo.argnames:
+        return
+    if any(
+        fixture_name in marker.args
+        for marker in metafunc.definition.iter_markers(name="usefixtures")
+    ):
+        return
+    if fixture_name in metafunc.fixturenames:
+        metafunc.fixturenames.remove(fixture_name)
+    if fixture_name in fixtureinfo.names_closure:
+        fixtureinfo.names_closure.remove(fixture_name)
+    fixtureinfo.name2fixturedefs.pop(fixture_name, None)
+
+
 @contextlib.contextmanager
 def _temporary_event_loop(loop: AbstractEventLoop) -> Iterator[None]:
     try:

tests/markers/test_event_loop_policy.py

@@ -0,0 +1,40 @@
+from textwrap import dedent
+
+from pytest import Pytester
+
+
+def test_parametrized_loop_policy_does_not_parametrize_sync_tests(
+    pytester: Pytester,
+):
+    pytester.makeini("[pytest]\nasyncio_default_fixture_loop_scope = function")
+    pytester.makepyfile(dedent("""\
+            import asyncio
+
+            import pytest
+
+            class CustomEventLoopPolicy(asyncio.DefaultEventLoopPolicy):
+                pass
+
+            @pytest.fixture(
+                params=[
+                    asyncio.DefaultEventLoopPolicy(),
+                    CustomEventLoopPolicy(),
+                ],
+            )
+            def event_loop_policy(request):
+                return request.param
+
+            @pytest.mark.asyncio
+            async def test_async():
+                assert isinstance(
+                    asyncio.get_event_loop_policy(),
+                    (asyncio.DefaultEventLoopPolicy, CustomEventLoopPolicy),
+                )
+
+            def test_sync():
+                assert True
+            """))
+
+    result = pytester.runpytest("--asyncio-mode=strict")
+
+    result.assert_outcomes(passed=3)