1 files changed, 49 insertions, 0 deletions
diff --git a/Lib/test/test_class.py b/Lib/test/test_class.py
index ecc01f2779..a916e878b7 100644
--- a/Lib/test/test_class.py
+++ b/Lib/test/test_class.py
@@ -595,5 +595,54 @@ class ClassTests(unittest.TestCase):
         with self.assertRaises(TypeError):
             type.__setattr__(A, b'x', None)
 
+    def testConstructorErrorMessages(self):
+        # bpo-31506: Improves the error message logic for object_new & object_init
+
+        # Class without any method overrides
+        class C:
+            pass
+
+        with self.assertRaisesRegex(TypeError, r'C\(\) takes no arguments'):
+            C(42)
+
+        with self.assertRaisesRegex(TypeError, r'C\(\) takes no arguments'):
+            C.__new__(C, 42)
+
+        with self.assertRaisesRegex(TypeError, r'C\(\).__init__\(\) takes no arguments'):
+            C().__init__(42)
+
+        with self.assertRaisesRegex(TypeError, r'C\(\) takes no arguments'):
+            object.__new__(C, 42)
+
+        with self.assertRaisesRegex(TypeError, r'C\(\).__init__\(\) takes no arguments'):
+            object.__init__(C(), 42)
+
+        # Class with both `__init__` & `__new__` method overriden
+        class D:
+            def __new__(cls, *args, **kwargs):
+                super().__new__(cls, *args, **kwargs)
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+
+        with self.assertRaisesRegex(TypeError, r'object.__new__\(\) takes no argument'):
+            D(42)
+
+        with self.assertRaisesRegex(TypeError, r'object.__new__\(\) takes no argument'):
+            D.__new__(D, 42)
+
+        with self.assertRaisesRegex(TypeError, r'object.__new__\(\) takes no argument'):
+            object.__new__(D, 42)
+
+        # Class that only overrides __init__
+        class E:
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+
+        with self.assertRaisesRegex(TypeError, r'object.__init__\(\) takes no argument'):
+            E().__init__(42)
+
+        with self.assertRaisesRegex(TypeError, r'object.__init__\(\) takes no argument'):
+            object.__init__(E(), 42)
+
 if __name__ == '__main__':
     unittest.main()