尝试模拟实例方法时的最大递归深度

Question

我想模拟一个实例方法。首先我想修改参数，然后我想调用原始方法。

我试过这个：

import mock
class Foo(object):
def my_method(data):
print(data)
def wrapped_method(data):
return Foo.my_method(data.replace('x', 'o'))
with mock.patch.object(Foo, 'my_method', wraps=wrapped_method):
foo = Foo()
foo.my_method('axe')  # should print "aoe"

但是我得到这个例外：

/home/foo/bin/python /home/foo/src/wrap-instance-method.py
Traceback (most recent call last):
File "/home/foo/src/wrap-instance-method.py", line 15, in <module>
foo.my_method('axe')  # should print "aoe"
File "/home/foo/local/lib/python2.7/site-packages/mock.py", line 955, in __call__
return _mock_self._mock_call(*args, **kwargs)
File "/home/foo/local/lib/python2.7/site-packages/mock.py", line 1024, in _mock_call
return self._mock_wraps(*args, **kwargs)
.....
return self._mock_wraps(*args, **kwargs)
File "/home/foo/src/wrap-instance-method.py", line 10, in wrapped_method
return Foo.my_method(data.replace('x', 'o'))
File "/home/foo/local/lib/python2.7/site-packages/mock.py", line 955, in __call__
return _mock_self._mock_call(*args, **kwargs)
File "/home/foo/local/lib/python2.7/site-packages/mock.py", line 960, in _mock_call
self.called = True
RuntimeError: maximum recursion depth exceeded while calling a Python object
Process finished with exit code 1

如何调用没有递归异常的原始方法？

Answer 1

您将Foo.my_method替换为调用Foo.my_method的方法，所以是的，您将获得无限递归。

如果必须拥有原始方法，则需要在修补之前存储它：

def mock_method_factory(original):
def wrapped_method(data):
return original(data.replace('x', 'o'))
return wrapped_method
with mock.patch.object(Foo, 'my_method', wraps=mock_method_factory(Foo.my_method)):
# ...

但是，wraps不处理绑定;original是一个未绑定的函数，wrapped_method不会在self中传递。

mock库可能不是这里的最佳选择。您本质上所做的是应用临时装饰器。子类Foo或手动将装饰器应用于Foo.my_method：

def mock_method_factory(original):
def wrapped_method(self, data):
return original(self, data.replace('x', 'o'))
return wrapped_method
class MockedFoo(Foo):
my_method = mock_method_factory(Foo.my_method)
foo = MockedFoo()
foo.my_method('axe')  # should print "aoe"

或

def mock_method_factory(original):
def wrapped_method(self, data):
return original(self, data.replace('x', 'o'))
return wrapped_method
original = Foo.my_method
try:
Foo.my_method = mock_method_factory(original)
foo = Foo()
foo.my_method('axe')  # should print "aoe"
finally:
Foo.my_method = original

Answer 2

我遇到了同样的问题。尝试使用Martijn的解决方案，但有自我问题。通过以下方式解决：

real_constructor = CLASS_NAME.__init__
def mock_constructor(self, **args):
return real_constructor.(self=self, **args)
with mock.patch.object(Foo, '__init__', side_effect=mock_constructor):
...