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# Copyright 2007 Google, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.
"""Unit tests for abc.py."""
import unittest
from test import support
import abc
from inspect import isabstract
class TestABC(unittest.TestCase):
def test_abstractmethod_basics(self):
@abc.abstractmethod
def foo(self): pass
self.assertTrue(foo.__isabstractmethod__)
def bar(self): pass
self.assertFalse(hasattr(bar, "__isabstractmethod__"))
def test_abstractproperty_basics(self):
@abc.abstractproperty
def foo(self): pass
self.assertTrue(foo.__isabstractmethod__)
def bar(self): pass
self.assertFalse(hasattr(bar, "__isabstractmethod__"))
class C(metaclass=abc.ABCMeta):
@abc.abstractproperty
def foo(self): return 3
class D(C):
@property
def foo(self): return super().foo
self.assertEqual(D().foo, 3)
def test_abstractmethod_integration(self):
for abstractthing in [abc.abstractmethod, abc.abstractproperty]:
class C(metaclass=abc.ABCMeta):
@abstractthing
def foo(self): pass # abstract
def bar(self): pass # concrete
self.assertEqual(C.__abstractmethods__, {"foo"})
self.assertRaises(TypeError, C) # because foo is abstract
self.assertTrue(isabstract(C))
class D(C):
def bar(self): pass # concrete override of concrete
self.assertEqual(D.__abstractmethods__, {"foo"})
self.assertRaises(TypeError, D) # because foo is still abstract
self.assertTrue(isabstract(D))
class E(D):
def foo(self): pass
self.assertEqual(E.__abstractmethods__, set())
E() # now foo is concrete, too
self.assertFalse(isabstract(E))
class F(E):
@abstractthing
def bar(self): pass # abstract override of concrete
self.assertEqual(F.__abstractmethods__, {"bar"})
self.assertRaises(TypeError, F) # because bar is abstract now
self.assertTrue(isabstract(F))
def test_type_has_no_abstractmethods(self):
# type pretends not to have __abstractmethods__.
self.assertRaises(AttributeError, getattr, type, "__abstractmethods__")
class meta(type):
pass
self.assertRaises(AttributeError, getattr, meta, "__abstractmethods__")
def test_metaclass_abc(self):
# Metaclasses can be ABCs, too.
class A(metaclass=abc.ABCMeta):
@abc.abstractmethod
def x(self):
pass
self.assertEqual(A.__abstractmethods__, {"x"})
class meta(type, A):
def x(self):
return 1
class C(metaclass=meta):
pass
def test_registration_basics(self):
class A(metaclass=abc.ABCMeta):
pass
class B(object):
pass
b = B()
self.assertFalse(issubclass(B, A))
self.assertFalse(issubclass(B, (A,)))
self.assertEqual(isinstance(b, A), False)
self.assertEqual(isinstance(b, (A,)), False)
A.register(B)
self.assertTrue(issubclass(B, A))
self.assertTrue(issubclass(B, (A,)))
self.assertEqual(isinstance(b, A), True)
self.assertEqual(isinstance(b, (A,)), True)
class C(B):
pass
c = C()
self.assertTrue(issubclass(C, A))
self.assertTrue(issubclass(C, (A,)))
self.assertEqual(isinstance(c, A), True)
self.assertEqual(isinstance(c, (A,)), True)
def test_isinstance_invalidation(self):
class A(metaclass=abc.ABCMeta):
pass
class B:
pass
b = B()
self.assertFalse(isinstance(b, A))
self.assertFalse(isinstance(b, (A,)))
A.register(B)
self.assertTrue(isinstance(b, A))
self.assertTrue(isinstance(b, (A,)))
def test_registration_builtins(self):
class A(metaclass=abc.ABCMeta):
pass
A.register(int)
self.assertEqual(isinstance(42, A), True)
self.assertEqual(isinstance(42, (A,)), True)
self.assertTrue(issubclass(int, A))
self.assertTrue(issubclass(int, (A,)))
class B(A):
pass
B.register(str)
class C(str): pass
self.assertEqual(isinstance("", A), True)
self.assertEqual(isinstance("", (A,)), True)
self.assertTrue(issubclass(str, A))
self.assertTrue(issubclass(str, (A,)))
self.assertTrue(issubclass(C, A))
self.assertTrue(issubclass(C, (A,)))
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
def test_register_non_class(self):
class A(metaclass=abc.ABCMeta):
pass
self.assertRaisesRegexp(TypeError, "Can only register classes",
A.register, 4)
def test_registration_transitiveness(self):
class A(metaclass=abc.ABCMeta):
pass
self.assertTrue(issubclass(A, A))
self.assertTrue(issubclass(A, (A,)))
class B(metaclass=abc.ABCMeta):
pass
self.assertFalse(issubclass(A, B))
self.assertFalse(issubclass(A, (B,)))
self.assertFalse(issubclass(B, A))
self.assertFalse(issubclass(B, (A,)))
class C(metaclass=abc.ABCMeta):
pass
A.register(B)
class B1(B):
pass
self.assertTrue(issubclass(B1, A))
self.assertTrue(issubclass(B1, (A,)))
class C1(C):
pass
B1.register(C1)
self.assertFalse(issubclass(C, B))
self.assertFalse(issubclass(C, (B,)))
self.assertFalse(issubclass(C, B1))
self.assertFalse(issubclass(C, (B1,)))
self.assertTrue(issubclass(C1, A))
self.assertTrue(issubclass(C1, (A,)))
self.assertTrue(issubclass(C1, B))
self.assertTrue(issubclass(C1, (B,)))
self.assertTrue(issubclass(C1, B1))
self.assertTrue(issubclass(C1, (B1,)))
C1.register(int)
class MyInt(int):
pass
self.assertTrue(issubclass(MyInt, A))
self.assertTrue(issubclass(MyInt, (A,)))
self.assertTrue(isinstance(42, A))
self.assertTrue(isinstance(42, (A,)))
def test_all_new_methods_are_called(self):
class A(metaclass=abc.ABCMeta):
pass
class B(object):
counter = 0
def __new__(cls):
B.counter += 1
return super().__new__(cls)
class C(A, B):
pass
self.assertEqual(B.counter, 0)
C()
self.assertEqual(B.counter, 1)
def test_main():
support.run_unittest(TestABC)
if __name__ == "__main__":
unittest.main()
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