Method test_issubclass_bad_arguments

Lib/test/test_abc.py:415–462

(self)

            self.assertIsInstance(42, (A,))

        def test_issubclass_bad_arguments(self):
            class A(metaclass=abc_ABCMeta):
                pass

            with self.assertRaises(TypeError):
                issubclass({}, A)  # unhashable

            with self.assertRaises(TypeError):
                issubclass(42, A)  # No __mro__

            # Python version supports any iterable as __mro__.
            # But it's implementation detail and don't emulate it in C version.
            class C:
                __mro__ = 42  # __mro__ is not tuple

            with self.assertRaises(TypeError):
                issubclass(C(), A)

            # bpo-34441: Check that issubclass() doesn't crash on bogus
            # classes.
            bogus_subclasses = [
                None,
                lambda x: [],
                lambda: 42,
                lambda: [42],
            ]

            for i, func in enumerate(bogus_subclasses):
                class S(metaclass=abc_ABCMeta):
                    __subclasses__ = func

                with self.subTest(i=i):
                    with self.assertRaises(TypeError):
                        issubclass(int, S)

            # Also check that issubclass() propagates exceptions raised by
            # __subclasses__.
            class CustomError(Exception): ...
            exc_msg = "exception from __subclasses__"

            def raise_exc():
                raise CustomError(exc_msg)

            class S(metaclass=abc_ABCMeta):
                __subclasses__ = raise_exc

            with self.assertRaisesRegex(CustomError, exc_msg):
                issubclass(int, S)

        def test_subclasshook(self):
            class A(metaclass=abc.ABCMeta):