[3.12] gh-84867: Do not load tests from TestCase and FunctionTestCase (GH-100497) (#109327)

gh-84867: Do not load tests from TestCase and FunctionTestCase (GH-100497)
(cherry picked from commit 66d1d7eb067d445f1ade151f4a6db3864dd9109f)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

1 files changed, 29 insertions, 0 deletions

diff --git a/Lib/test/test_unittest/test_loader.py b/Lib/test/test_unittest/test_loader.py
index a203145..9fc0d95 100644
--- a/Lib/test/test_unittest/test_loader.py
+++ b/Lib/test/test_unittest/test_loader.py
@@ -82,6 +82,22 @@ class Test_TestLoader(unittest.TestCase):
         self.assertIsInstance(suite, loader.suiteClass)
         self.assertEqual(list(suite), [Foo('runTest')])
 
+    # "Do not load any tests from `TestCase` class itself."
+    def test_loadTestsFromTestCase__from_TestCase(self):
+        loader = unittest.TestLoader()
+
+        suite = loader.loadTestsFromTestCase(unittest.TestCase)
+        self.assertIsInstance(suite, loader.suiteClass)
+        self.assertEqual(list(suite), [])
+
+    # "Do not load any tests from `FunctionTestCase` class."
+    def test_loadTestsFromTestCase__from_FunctionTestCase(self):
+        loader = unittest.TestLoader()
+
+        suite = loader.loadTestsFromTestCase(unittest.FunctionTestCase)
+        self.assertIsInstance(suite, loader.suiteClass)
+        self.assertEqual(list(suite), [])
+
     ################################################################
     ### /Tests for TestLoader.loadTestsFromTestCase
 
@@ -103,6 +119,19 @@ class Test_TestLoader(unittest.TestCase):
         expected = [loader.suiteClass([MyTestCase('test')])]
         self.assertEqual(list(suite), expected)
 
+    # "This test ensures that internal `TestCase` subclasses are not loaded"
+    def test_loadTestsFromModule__TestCase_subclass_internals(self):
+        # See https://github.com/python/cpython/issues/84867
+        m = types.ModuleType('m')
+        # Simulate imported names:
+        m.TestCase = unittest.TestCase
+        m.FunctionTestCase = unittest.FunctionTestCase
+
+        loader = unittest.TestLoader()
+        suite = loader.loadTestsFromModule(m)
+        self.assertIsInstance(suite, loader.suiteClass)
+        self.assertEqual(list(suite), [])
+
     # "This method searches `module` for classes derived from TestCase"
     #
     # What happens if no tests are found (no TestCase instances)?