unittesting：修补对象__base__

Question

从this question开始，我尝试使用A()修补课程Mock()，以便在初始化B()时，将Mock用作基础，例如：

class A(object): ...
class B(A): ...

def setUp(self):
    with patch('A', new_callable=Mock) as MockObject:
        self.b = B()
        self.b.__class__.__base__ = MockOjbect

哪个不起作用，因为 base 是只读的。这样做的正确方法是什么？

更新

>>> from mock import Mock
>>> class A(object):
...     pass
... 
>>> class B(A):
...     pass
... 
>>> b.__class__.__bases__ = (Mock, )
>>> b.__class__.__bases__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/envs/myenv/local/lib/python2.7/site-packages/mock.py", line 656, in __getattr__
    elif self._mock_methods is not None:
  File "/opt/envs/myenv/local/lib/python2.7/site-packages/mock.py", line 655, in __getattr__
    raise AttributeError(name)
AttributeError: _mock_methods

要说清楚，我不相信这是实现我想要做的最好的方式，我一半希望别人会想出另一种方式。

Answer 1

__bases__是tuple。

更正版本：

class A(object): ...
class B(A): ...

def setUp(self):
    with patch('A', new_callable=Mock) as MockObject:
        self.b = B()
        self.b.__class__.__bases__ = (MockOjbect,)

请参阅：

>>> class Foo(object):
...     pass
... 
>>> Foo.__class__.__bases__
(<type 'object'>,)

tuple是不可变的，但__bases__属性肯定不是只读的。