Deprecate event_loop_policy fixture

changelog.d/1419.deprecated.rst

@@ -0,0 +1 @@
+Overriding the *event_loop_policy* fixture is deprecated. Use the ``pytest_asyncio_loop_factories`` hook instead.

docs/how-to-guides/multiple_loops.rst

@@ -2,6 +2,10 @@
 How to test with different event loops
 ======================================
 
+.. warning::
+
+   Overriding the *event_loop_policy* fixture is deprecated and will be removed in a future version of pytest-asyncio. Use the ``pytest_asyncio_loop_factories`` hook instead. See :doc:`custom_loop_factory` for details.
+
 Parametrizing the *event_loop_policy* fixture parametrizes all async tests. The following example causes all async tests to run multiple times, once for each event loop in the fixture parameters:
 
 .. include:: multiple_loops_example.py

docs/how-to-guides/uvloop.rst

@@ -24,7 +24,7 @@ Using the event_loop_policy fixture
 
 .. note::
 
-   ``asyncio.AbstractEventLoopPolicy`` is deprecated as of Python 3.14 (removal planned for 3.16), and ``uvloop.EventLoopPolicy`` will be removed alongside it. Prefer the hook approach above.
+   ``asyncio.AbstractEventLoopPolicy`` is deprecated as of Python 3.14 (removal planned for 3.16), and ``uvloop.EventLoopPolicy`` will be removed alongside it. Overriding the *event_loop_policy* fixture is also deprecated in pytest-asyncio. Prefer the hook approach above.
 
 For older versions of Python and uvloop, you can override the *event_loop_policy* fixture in your *conftest.py:*
 

docs/reference/fixtures/index.rst

@@ -4,6 +4,11 @@ Fixtures
 
 event_loop_policy
 =================
+
+.. warning::
+
+   Overriding the *event_loop_policy* fixture is deprecated and will be removed in a future version of pytest-asyncio. Use the ``pytest_asyncio_loop_factories`` hook instead. See :doc:`../hooks` for details.
+
 Returns the event loop policy used to create asyncio event loops.
 The default return value is *asyncio.get_event_loop_policy().*
 

pytest_asyncio/plugin.py

@@ -919,6 +919,13 @@ def inner(*args, **kwargs):
 
 @pytest.hookimpl(wrapper=True)
 def pytest_fixture_setup(fixturedef: FixtureDef, request) -> object | None:
+    if (
+        fixturedef.argname == "event_loop_policy"
+        and fixturedef.func.__module__ != __name__
+    ):
+        warnings.warn(
+            PytestDeprecationWarning(_EVENT_LOOP_POLICY_FIXTURE_DEPRECATION_WARNING),
+        )
     asyncio_mode = _get_asyncio_mode(request.config)
     if not _is_asyncio_fixture_function(fixturedef.func):
         if asyncio_mode == Mode.STRICT:
@@ -962,6 +969,12 @@ def pytest_fixture_setup(fixturedef: FixtureDef, request) -> object | None:
 mark.asyncio 'loop_factories' must be a non-empty sequence of strings.
 """
 
+_EVENT_LOOP_POLICY_FIXTURE_DEPRECATION_WARNING = """\
+Overriding the "event_loop_policy" fixture is deprecated \
+and will be removed in a future version of pytest-asyncio. \
+Use the "pytest_asyncio_loop_factories" hook to customize event loop creation.\
+"""
+
 
 def _parse_asyncio_marker(
     asyncio_marker: Mark,

tests/markers/test_class_scope.py

@@ -133,7 +133,7 @@ async def test_does_not_use_custom_event_loop_policy():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=3)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)
@@ -168,7 +168,7 @@ async def test_parametrized_loop(self, request):
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=2)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)

tests/markers/test_function_scope.py

@@ -107,7 +107,7 @@ async def test_uses_custom_event_loop_policy():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=1, warnings=2)
+        result.assert_outcomes(passed=1, warnings=3)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=1)
@@ -148,12 +148,57 @@ async def test_parametrized_loop():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=3)
+        result.assert_outcomes(passed=2, warnings=5)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)
 
 
+def test_event_loop_policy_fixture_override_emits_deprecation_warning(
+    pytester: Pytester,
+):
+    pytester.makeini("[pytest]\nasyncio_default_fixture_loop_scope = function")
+    pytester.makepyfile(
+        dedent("""\
+            import asyncio
+            import pytest
+
+            pytestmark = pytest.mark.asyncio
+
+            @pytest.fixture
+            def event_loop_policy():
+                return asyncio.DefaultEventLoopPolicy()
+
+            async def test_anything():
+                pass
+            """),
+    )
+    result = pytester.runpytest("--asyncio-mode=strict", "-W", "default")
+    result.assert_outcomes(passed=1)
+    result.stdout.fnmatch_lines(
+        "*PytestDeprecationWarning*event_loop_policy*deprecated*"
+    )
+
+
+def test_default_event_loop_policy_fixture_does_not_warn(
+    pytester: Pytester,
+):
+    pytester.makeini("[pytest]\nasyncio_default_fixture_loop_scope = function")
+    pytester.makepyfile(
+        dedent("""\
+            import pytest
+
+            pytestmark = pytest.mark.asyncio
+
+            async def test_anything():
+                pass
+            """),
+    )
+    result = pytester.runpytest("--asyncio-mode=strict", "-W", "default")
+    result.assert_outcomes(passed=1)
+    result.stdout.no_fnmatch_line("*PytestDeprecationWarning*event_loop_policy*")
+
+
 def test_asyncio_mark_provides_function_scoped_loop_to_fixtures(
     pytester: Pytester,
 ):

tests/markers/test_module_scope.py

@@ -83,7 +83,7 @@ async def test_does_not_use_custom_event_loop_policy():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=3)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)
@@ -118,7 +118,7 @@ async def test_parametrized_loop():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=2)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)

tests/markers/test_package_scope.py

@@ -115,7 +115,7 @@ async def test_also_uses_custom_event_loop_policy():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=3)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)
@@ -153,7 +153,7 @@ async def test_parametrized_loop():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=2)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)

tests/markers/test_session_scope.py

@@ -116,7 +116,7 @@ async def test_also_uses_custom_event_loop_policy():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=3)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)
@@ -154,7 +154,7 @@ async def test_parametrized_loop():
         pytest_args.extend(["-W", "default"])
     result = pytester.runpytest(*pytest_args)
     if sys.version_info >= (3, 14):
-        result.assert_outcomes(passed=2, warnings=2)
+        result.assert_outcomes(passed=2, warnings=4)
         result.stdout.fnmatch_lines("*DefaultEventLoopPolicy*")
     else:
         result.assert_outcomes(passed=2)