Using PR 14415, the following test of test_multiprocessing_spawn emits a false alarm because multiprocessing use "Finalizer" objects which are only finalized "later":
test.test_multiprocessing_spawn.WithManagerTestMyManager.test_mymanager_context_prestarted


Workaround, call explicitly _run_finalizers():

diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index eef262d723..bfecbab9ee 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -5651,6 +5651,7 @@ def install_tests_in_module_dict(remote_globs, start_method):
         if need_sleep:
             time.sleep(0.5)
         multiprocessing.process._cleanup()
+        multiprocessing.util._run_finalizers()
         test.support.gc_collect()
 
     remote_globs['setUpModule'] = setUpModule