From e8ed3a8c55801d72a0cf8e563c7e3f2fd7649d68 Mon Sep 17 00:00:00 2001
From: Russell Keith-Magee <russell@keith-magee.com>
Date: Tue, 18 Mar 2025 08:15:05 +0800
Subject: [PATCH 1/3] Ensure PDB cleans up event loop policies after using
 asyncio.

---
 Lib/test/test_pdb.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 8cd634426bd88b..cd3e2dc7ba2c27 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -13,6 +13,7 @@
 import zipapp
 import zipfile
 
+from asyncio.events import _set_event_loop_policy
 from contextlib import ExitStack, redirect_stdout
 from io import StringIO
 from test import support
@@ -41,6 +42,10 @@ def __exit__(self, *exc):
         if self.orig_trace:
             sys.settrace(self.orig_trace)
 
+        # To prevent a warning "test altered the execution environment" if
+        # asyncio features are used.
+        _set_event_loop_policy(None)
+
 
 def test_pdb_displayhook():
     """This tests the custom displayhook for pdb.

From 6c794e0a325270607480920ed6088581ae6ae92b Mon Sep 17 00:00:00 2001
From: Russell Keith-Magee <russell@keith-magee.com>
Date: Tue, 18 Mar 2025 14:52:27 +0800
Subject: [PATCH 2/3] Perform asyncio cleanup as part of Doctest teardown.

---
 Lib/test/test_pdb.py | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index cd3e2dc7ba2c27..28c3e1244eedae 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -42,10 +42,6 @@ def __exit__(self, *exc):
         if self.orig_trace:
             sys.settrace(self.orig_trace)
 
-        # To prevent a warning "test altered the execution environment" if
-        # asyncio features are used.
-        _set_event_loop_policy(None)
-
 
 def test_pdb_displayhook():
     """This tests the custom displayhook for pdb.
@@ -4675,13 +4671,33 @@ def func():
 
 def load_tests(loader, tests, pattern):
     from test import test_pdb
+
     def setUpPdbBackend(backend):
         def setUp(test):
             import pdb
             pdb.set_default_backend(backend)
         return setUp
-    tests.addTest(doctest.DocTestSuite(test_pdb, setUp=setUpPdbBackend('monitoring')))
-    tests.addTest(doctest.DocTestSuite(test_pdb, setUp=setUpPdbBackend('settrace')))
+
+    def tearDown(test):
+        # Ensure that asyncio state has been cleared at the end of the test.
+        # This prevents a "test altered the execution environment" warning if
+        # asyncio features are used.
+        _set_event_loop_policy(None)
+
+    tests.addTest(
+        doctest.DocTestSuite(
+            test_pdb,
+            setUp=setUpPdbBackend('monitoring'),
+            tearDown=tearDown,
+        )
+    )
+    tests.addTest(
+        doctest.DocTestSuite(
+            test_pdb,
+            setUp=setUpPdbBackend('settrace'),
+            tearDown=tearDown,
+        )
+    )
     return tests
 
 

From 584aa2b28cbd1662a8b54fa3bad0e85f32dcbe1a Mon Sep 17 00:00:00 2001
From: Russell Keith-Magee <russell@keith-magee.com>
Date: Wed, 19 Mar 2025 07:06:59 +0800
Subject: [PATCH 3/3] Modify asyncio.run usage to cleanup at time of use.

---
 Lib/test/test_pdb.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 28c3e1244eedae..18fb94af479527 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -2155,7 +2155,7 @@ def test_pdb_asynctask():
             ...     import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
 
             >>> def test_function():
-            ...     asyncio.run(test())
+            ...     asyncio.run(test(), loop_factory=asyncio.EventLoop)
 
             >>> with PdbTestInput([  # doctest: +ELLIPSIS
             ...     '$_asynctask',