PYTHON-4745 - Document and Test Behavior when User Cancels Async Operation

Author: NoahStapp

test/asynchronous/test_async_cancellation.py

@@ -0,0 +1,40 @@
+# Copyright 2025-present MongoDB, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Test that async cancellation performed by users raises the expected error."""
+from __future__ import annotations
+
+import asyncio
+import sys
+
+sys.path[0:0] = [""]
+
+from test.asynchronous import AsyncIntegrationTest
+
+
+class TestAsyncCancellation(AsyncIntegrationTest):
+    async def test_async_cancellation(self):
+        async def task():
+            while True:
+                await self.client.db.test.insert_one({"x": 1})
+                await asyncio.sleep(0.005)
+
+        task = asyncio.create_task(task())
+
+        # Make sure the task successfully runs a few operations to simulate a long-running user task
+        await asyncio.sleep(0.01)
+
+        task.cancel()
+        with self.assertRaises(asyncio.CancelledError):
+            await task

tools/synchro.py

@@ -168,7 +168,7 @@
 
 def async_only_test(f: str) -> bool:
     """Return True for async tests that should not be converted to sync."""
-    return f in ["test_locks.py", "test_concurrency.py"]
+    return f in ["test_locks.py", "test_concurrency.py", "test_async_cancellation.py"]
 
 
 test_files = [