模擬修補類中不存在的函數

Question

使用Python的mock框架，是否有可能修補修補類中不存在的函數。如果是這樣，怎麼樣？

例如：

example.py

import mock 
import unittest 


class MyClass(object): 
    pass 


class MyTests(unittest.TestCase): 

    def test_mock_non_existent_function(self): 
     with mock.patch('example.MyClass.my_function'): 
      pass 

運行該測試引發錯誤：

Error 
Traceback (most recent call last): 
    File "/Users/jesse/Code/my_proj/lib/mock.py", line 1193, in patched 
    File "/Users/jesse/Code/my_proj/lib/mock.py", line 1268, in __enter__ 
    File "/Users/jesse/Code/my_proj/lib/mock.py", line 1242, in get_original 
AttributeError: <class 'example.MyClass'> does not have the attribute 'my_function' 

使用Python 2.7.9和mock 1.0.1。

Answer 1

您需要指定要以某種方式打補丁的功能。 從mock docs：

>>> class Class(object): 
...  def method(self): 
...   pass 
... 
>>> with patch('__main__.Class') as MockClass: 
...  instance = MockClass.return_value 
...  instance.method.return_value = 'foo' 
...  assert Class() is instance 
...  assert Class().method() == 'foo' 
...