Method test_mutable_bases

Lib/test/test_descr.py:4156–4344

(self)

                               int().__rpow__, 1, 2, 3)

    def test_mutable_bases(self):
        # Testing mutable bases...

        # stuff that should work:
        class C(object):
            pass
        class C2(object):
            def __getattribute__(self, attr):
                if attr == 'a':
                    return 2
                else:
                    return super(C2, self).__getattribute__(attr)
            def meth(self):
                return 1
        class D(C):
            pass
        class E(D):
            pass
        d = D()
        e = E()
        D.__bases__ = (C,)
        D.__bases__ = (C2,)
        self.assertEqual(d.meth(), 1)
        self.assertEqual(e.meth(), 1)
        self.assertEqual(d.a, 2)
        self.assertEqual(e.a, 2)
        self.assertEqual(C2.__subclasses__(), [D])

        with self.assertRaisesRegex(TypeError,
                    "cannot delete '__bases__' attribute of type 'D'"):
            del D.__bases__
        with self.assertRaisesRegex(TypeError, 'can only assign non-empty tuple'):
            D.__bases__ = ()
        with self.assertRaisesRegex(TypeError, 'can only assign tuple'):
            D.__bases__ = [C]
        with self.assertRaisesRegex(TypeError, 'duplicate base class'):
            D.__bases__ = (C, C)
        with self.assertRaisesRegex(TypeError, 'inheritance cycle'):
            D.__bases__ = (D,)
        with self.assertRaisesRegex(TypeError, 'inheritance cycle'):
            D.__bases__ = (E,)

        class A:
            __slots__ = ()
            def __repr__(self):
                return '<A>'
        class A_with_dict:
            __slots__ = ('__dict__',)
            def __repr__(self):
                return '<A_with_dict>'
        class A_with_dict_weakref:
            def __repr__(self):
                return '<A_with_dict_weakref>'
        class A_with_slots:
            __slots__ = ('x',)
            def __repr__(self):
                return '<A_with_slots>'
        class A_with_slots_dict: