[Python-checkins] GH-95736: fix IsolatedAsyncioTestCase to initialize Runner before calling setup functions (#95898)

[gvanrossum]

https://github.com/python/cpython/commit/9d515997f943b7b510268448f372dabcbf957858
commit: 9d515997f943b7b510268448f372dabcbf957858
branch: main
author: Kumar Aditya <59607654+kumaraditya303 at users.noreply.github.com>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2022-08-16T08:52:06-07:00
summary:

GH-95736: fix IsolatedAsyncioTestCase to initialize Runner before calling setup functions  (#95898)

files:
A Misc/NEWS.d/next/Library/2022-08-11-18-22-29.gh-issue-95736.LzRZXe.rst
M Lib/test/test_unittest/test_async_case.py
M Lib/unittest/async_case.py

diff --git a/Lib/test/test_unittest/test_async_case.py b/Lib/test/test_unittest/test_async_case.py
index beadcac070b4..f59fc760d381 100644
--- a/Lib/test/test_unittest/test_async_case.py
+++ b/Lib/test/test_unittest/test_async_case.py
@@ -434,6 +434,21 @@ async def cleanup(self, fut):
         test.doCleanups()
         self.assertEqual(events, ['asyncSetUp', 'test', 'cleanup'])
 
+    def test_setup_get_event_loop(self):
+        # See https://github.com/python/cpython/issues/95736
+        # Make sure the default event loop is not used
+        asyncio.set_event_loop(None)
+
+        class TestCase1(unittest.IsolatedAsyncioTestCase):
+            def setUp(self):
+                asyncio.get_event_loop_policy().get_event_loop()
+
+            async def test_demo1(self):
+                pass
+
+        test = TestCase1('test_demo1')
+        result = test.run()
+        self.assertTrue(result.wasSuccessful())
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/unittest/async_case.py b/Lib/unittest/async_case.py
index a90eed98f871..8b06fad06209 100644
--- a/Lib/unittest/async_case.py
+++ b/Lib/unittest/async_case.py
@@ -116,6 +116,10 @@ def _setupAsyncioRunner(self):
         assert self._asyncioRunner is None, 'asyncio runner is already initialized'
         runner = asyncio.Runner(debug=True)
         self._asyncioRunner = runner
+        # Force loop to be initialized and set as the current loop
+        # so that setUp functions can use get_event_loop() and get the
+        # correct loop instance.
+        runner.get_loop()
 
     def _tearDownAsyncioRunner(self):
         runner = self._asyncioRunner
diff --git a/Misc/NEWS.d/next/Library/2022-08-11-18-22-29.gh-issue-95736.LzRZXe.rst b/Misc/NEWS.d/next/Library/2022-08-11-18-22-29.gh-issue-95736.LzRZXe.rst
new file mode 100644
index 000000000000..abc270fe35ca
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-08-11-18-22-29.gh-issue-95736.LzRZXe.rst
@@ -0,0 +1 @@
+Fix :class:`unittest.IsolatedAsyncioTestCase` to set event loop before calling setup functions. Patch by Kumar Aditya.