From 404894a84ac95c8c40220957f68e6fed6bd6fd45 Mon Sep 17 00:00:00 2001
From: "Gregory P. Smith [Google]" <greg@krypto.org>
Date: Tue, 19 Apr 2022 04:18:42 +0000
Subject: [PATCH 1/2] unittest.IsolatedAsyncioTestCase no longer leaks its
 executor.

For things like test_asyncio.test_thread this was causing frequent
"environment modified by test" errors as the executor threads had not
always stopped running after the test was over.
---
 Lib/unittest/async_case.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Lib/unittest/async_case.py b/Lib/unittest/async_case.py
index 23231199f98706..d9c694e368255d 100644
--- a/Lib/unittest/async_case.py
+++ b/Lib/unittest/async_case.py
@@ -148,6 +148,8 @@ def _tearDownAsyncioLoop(self):
             # shutdown asyncgens
             loop.run_until_complete(loop.shutdown_asyncgens())
         finally:
+            # Prevent our executor environment from leaking to future tests.
+            loop.run_until_complete(loop.shutdown_default_executor())
             asyncio.set_event_loop(None)
             loop.close()
 

From 522e6e4c2e8b38331fed9c9a7a069e31ba950ada Mon Sep 17 00:00:00 2001
From: "Gregory P. Smith [Google]" <greg@krypto.org>
Date: Tue, 19 Apr 2022 04:33:42 +0000
Subject: [PATCH 2/2] News entry.

---
 .../Library/2022-04-19-04-33-39.gh-issue-91676.ceQBwh.rst     | 4 ++++
 1 file changed, 4 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2022-04-19-04-33-39.gh-issue-91676.ceQBwh.rst

diff --git a/Misc/NEWS.d/next/Library/2022-04-19-04-33-39.gh-issue-91676.ceQBwh.rst b/Misc/NEWS.d/next/Library/2022-04-19-04-33-39.gh-issue-91676.ceQBwh.rst
new file mode 100644
index 00000000000000..dfbaef4440e0a6
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-04-19-04-33-39.gh-issue-91676.ceQBwh.rst
@@ -0,0 +1,4 @@
+Fix :class:`unittest.IsolatedAsyncioTestCase` to shutdown the per test event
+loop executor before returning from its ``run`` method so that a not yet
+stopped or garbage collected executor state does not persist beyond the
+test.