Fixed #31944 -- Used addCleanup() to register TestContextDecorator cleanups.

Cleanups from addCleanup() are scheduled to happen in reverse order to
the order they are added (LIFO). Ensures each cleanup is executed from
the innermost to the outermost.

tests/test_utils/tests.py

@@ -1477,4 +1477,27 @@ class TestContextDecoratorTests(SimpleTestCase):
         self.assertFalse(mock_disable.called)
         with self.assertRaisesMessage(NotImplementedError, 'reraised'):
             decorated_test_class.setUp()
+        decorated_test_class.doCleanups()
         self.assertTrue(mock_disable.called)
+
+    def test_cleanups_run_after_tearDown(self):
+        calls = []
+
+        class SaveCallsDecorator(TestContextDecorator):
+            def enable(self):
+                calls.append('enable')
+
+            def disable(self):
+                calls.append('disable')
+
+        class AddCleanupInSetUp(unittest.TestCase):
+            def setUp(self):
+                calls.append('setUp')
+                self.addCleanup(lambda: calls.append('cleanup'))
+
+        decorator = SaveCallsDecorator()
+        decorated_test_class = decorator.__call__(AddCleanupInSetUp)()
+        decorated_test_class.setUp()
+        decorated_test_class.tearDown()
+        decorated_test_class.doCleanups()
+        self.assertEqual(calls, ['enable', 'setUp', 'cleanup', 'disable'])