test_abc.py 文件源码

def test_registration_edge_cases(self):
        class A(metaclass=abc.ABCMeta):
            pass
        A.register(A)  # should pass silently
        class A1(A):
            pass
        self.assertRaises(RuntimeError, A1.register, A)  # cycles not allowed
        class B(object):
            pass
        A1.register(B)  # ok
        A1.register(B)  # should pass silently
        class C(A):
            pass
        A.register(C)  # should pass silently
        self.assertRaises(RuntimeError, C.register, A)  # cycles not allowed
        C.register(B)  # ok