PYTHON-4648 Fix handling of event_loop_policy in tests (mongodb#1799)

Author: blink1073

test/__init__.py

@@ -79,16 +79,6 @@
 
 _IS_SYNC = True
 
-# The default asyncio loop implementation on Windows
-# has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
-# We explicitly use a different loop implementation here to prevent that issue
-if (
-    not _IS_SYNC
-    and sys.platform == "win32"
-    and asyncio.get_event_loop_policy() == asyncio.WindowsProactorEventLoopPolicy
-):
-    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())  # type: ignore[attr-defined]
-
 
 class ClientContext:
     client: MongoClient

test/asynchronous/__init__.py

@@ -79,16 +79,6 @@
 
 _IS_SYNC = False
 
-# The default asyncio loop implementation on Windows
-# has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
-# We explicitly use a different loop implementation here to prevent that issue
-if (
-    not _IS_SYNC
-    and sys.platform == "win32"
-    and asyncio.get_event_loop_policy() == asyncio.WindowsProactorEventLoopPolicy
-):
-    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())  # type: ignore[attr-defined]
-
 
 class AsyncClientContext:
     client: AsyncMongoClient

test/asynchronous/conftest.py

@@ -1,13 +1,27 @@
 from __future__ import annotations
 
+import asyncio
+import sys
 from test import pytest_conf
 from test.asynchronous import async_setup, async_teardown
 
+import pytest
 import pytest_asyncio
 
 _IS_SYNC = False
 
 
+@pytest.fixture(scope="session")
+def event_loop_policy():
+    # The default asyncio loop implementation on Windows
+    # has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
+    # We explicitly use a different loop implementation here to prevent that issue
+    if sys.platform == "win32":
+        return asyncio.WindowsSelectorEventLoopPolicy()  # type: ignore[attr-defined]
+
+    return asyncio.get_event_loop_policy()
+
+
 @pytest_asyncio.fixture(scope="session", autouse=True)
 async def test_setup_and_teardown():
     await async_setup()

test/conftest.py

@@ -1,12 +1,25 @@
 from __future__ import annotations
 
+import asyncio
+import sys
 from test import pytest_conf, setup, teardown
 
 import pytest
 
 _IS_SYNC = True
 
 
+@pytest.fixture(scope="session")
+def event_loop_policy():
+    # The default asyncio loop implementation on Windows
+    # has issues with sharing sockets across loops (https://github.com/python/cpython/issues/122240)
+    # We explicitly use a different loop implementation here to prevent that issue
+    if sys.platform == "win32":
+        return asyncio.WindowsSelectorEventLoopPolicy()  # type: ignore[attr-defined]
+
+    return asyncio.get_event_loop_policy()
+
+
 @pytest.fixture(scope="session", autouse=True)
 def test_setup_and_teardown():
     setup()