如何在不改变其行为的情况下检查是否调用了 @patched-out python 方法? [英] How can I check if a @patched-out python method is called, without changing its behavior?

问题描述

我一直在使用 python mock 模块为我的测试用例.我经常用 @patch('my_method') 装饰器装饰我的测试用例.然后在测试用例的主体中，我在修补的方法上设置 .return_value 属性或 .side_effect 属性以模拟其行为.同样在测试用例中，我检查修补后的方法是否使用 .assert_call_once() 调用.这工作正常.没问题.示例:

I've been using the python mock module for my test-cases. Frequently I decorate my test cases with the @patch('my_method') decorator. Then in the body of the test-case, I set the .return_value attribute or the .side_effect attribute on the patched-out method to simulate its behavior. Also in the test case, I check that the patched-out method was called with .assert_called_once(). This works fine. No problems. Example:

from mock import patch

@patch('my_method')
def test_case_1(self, mock_my_method):
    mock_my_method.return_value = None
    # Do some testing here
    mock_my_method.assert_called_once()

现在我想做一些稍微不同的事情:我只想检查一个修补过的方法是否被调用过一次(通过使用 .assert_called_once().然而，我不想改变方法的行为，也不想指定一个假的返回值.我该怎么做?

Now I want to do something slightly different: I only want to check that a patched-out method was called once (by using .assert_called_once(). However, I don't want to change the method's behavior nor do I want to specify a fake return value. How can I do that?

推荐答案

如果您只想将 patch 用于其调用记录功能，而不模拟原始函数的行为，则指定原始函数作为模拟的 side_effect 函数:

If you want to use patch just for its call-logging functionality, without mocking out the original function's behavior, then specify the original function as the side_effect of the mock:

@patch('my_function', side_effect=my_function)
...

side_effect 名称具有误导性.如果模拟有 side_effect 函数，调用模拟将调用 side_effect 并返回或引发 side_effect 返回或引发的任何内容.使用原始函数作为 side_effect 意味着我们得到原始函数的行为.(side_effect 可以是除了函数之外的其他几种东西，但我们在这里不需要那个功能.)

The side_effect name is misleading. If a mock has a side_effect function, calling the mock will call the side_effect and return or raise whatever the side_effect returns or raises. Using the original function as side_effect means we get the original function's behavior. (side_effect can be a few other kinds of thing besides functions, but we don't need that functionality here.)

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