PYTHON-4784 - Add tests to confirm async parallelism

test/asynchronous/test_concurrency.py

@@ -0,0 +1,54 @@
+# Copyright 2024-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.
+
+"""Tests to ensure that the async API is properly concurrent with asyncio."""
+from __future__ import annotations
+
+import asyncio
+import time
+from test.asynchronous import AsyncIntegrationTest, async_client_context
+from test.utils import delay
+
+_IS_SYNC = False
+
+
+class TestAsyncConcurrency(AsyncIntegrationTest):
+    async def _task(self, client):
+        await client.db.test.find_one({"$where": delay(0.20)})
+
+    async def test_concurrency(self):
+        tasks = []
+        iterations = 5
+
+        client = await self.async_single_client()
+        await client.db.test.drop()
+        await client.db.test.insert_one({"x": 1})
+
+        start = time.time()
+
+        for _ in range(iterations):
+            await self._task(client)
+
+        sequential_time = time.time() - start
+        start = time.time()
+
+        for i in range(iterations):
+            tasks.append(self._task(client))
+
+        await asyncio.gather(*tasks)
+        concurrent_time = time.time() - start
+
+        percent_faster = (sequential_time - concurrent_time) / concurrent_time * 100
+        # We expect the concurrent tasks to be at least 75% faster on all platforms as a conservative benchmark
+        self.assertGreaterEqual(percent_faster, 75)

tools/synchro.py

@@ -152,7 +152,7 @@
 
 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"]
+    return f in ["test_locks.py", "test_concurrency.py"]
 
 
 test_files = [