GH-95899: fix asyncio.Runner to call set_event_loop only once (GH-95900) (#96003)

(cherry picked from commit 914f6367a0d015986dafa7a9d542e24192753b6b)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/Lib/test/test_asyncio/test_runners.py b/Lib/test/test_asyncio/test_runners.py
index 5e1db23..4e3acb9 100644
--- a/Lib/test/test_asyncio/test_runners.py
+++ b/Lib/test/test_asyncio/test_runners.py
@@ -456,6 +456,20 @@ class RunnerTests(BaseTest):
             ):
                 runner.run(coro())
 
+    def test_set_event_loop_called_once(self):
+        # See https://github.com/python/cpython/issues/95736
+        async def coro():
+            pass
+
+        policy = asyncio.get_event_loop_policy()
+        policy.set_event_loop = mock.Mock()
+        runner = asyncio.Runner()
+        runner.run(coro())
+        runner.run(coro())
+
+        self.assertEqual(1, policy.set_event_loop.call_count)
+        runner.close()
+
 
 if __name__ == '__main__':
     unittest.main()