gh-125252: Added support unittest.TestCase of multiple-inheritance co…

Lib/test/test_unittest/test_case.py

@@ -637,6 +637,27 @@ def run(self, result):
         self.assertIs(retval, resultOut)
 
 
+    # This test verifies that cooperative multiple inheritance works correctly
+    # when unittest.TestCase is combined with another class.
+    def test_init_support_cooperative_multiple_inheritance(self):
+        class Base:
+            def __init__(self):
+                super().__init__()
+                self.base_initialized = True
+
+        class Foo(unittest.TestCase, Base):
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+                self.testcase_initialized = True
+
+            def test_inheritance(self):
+                self.assertTrue(self.base_initialized)
+                self.assertTrue(self.testcase_initialized)
+
+        result = Foo('test_inheritance').run()
+        self.assertTrue(result.wasSuccessful())
+
+
     def testShortDescriptionWithoutDocstring(self):
         self.assertIsNone(self.shortDescription())
 

Lib/unittest/case.py

@@ -413,6 +413,9 @@ def __init__(self, methodName='runTest'):
            method when executed. Raises a ValueError if the instance does
            not have a method with the specified name.
         """
+
+        super(TestCase, self).__init__()
+
         self._testMethodName = methodName
         self._outcome = None
         self._testMethodDoc = 'No test'

Misc/NEWS.d/next/Library/2024-10-11-01-48-04.gh-issue-125252.2hX3Pb.rst

@@ -0,0 +1,2 @@
+Added support :class:`unittest.TestCase` of multiple-inheritance
+cooperative.