unittest.Mock-结合return_value和side_effect [英] unittest.Mock - Combining return_value and side_effect

问题描述

是否有可能使Mock对象在调用时返回值并在调用时执行语句?例如:

Is it possible to have a Mock object return a value when called as well as execute a statement when called? For example this:

> mocked_func = Mock(return_value='Returned foo', 
                     side_effect=lambda: print('Side effect executed')
                    )

> print(mocked_func())

Side effect executed
None

这里的文档似乎有点模棱两可，但在我看来，当使用side_effect时，将完全忽略return_value，并且仅返回side_effect函数的结果(在print()情况下为None).

The documentation seems a little ambiguous here but it seems to me that when side_effect is used, then return_value is ignored altogether and only the result of side_effect function is returned (which in case of print() is None).

由于Python并不真正支持多语句lambda(AFAIK，最好的办法是将表达式放在元组中，但随后将返回整个元组)-是否可以将两个参数组合在一起?

Since Python does not really support multi-statement lambdas (AFAIK, the best you can do is put expressions in a tuple, but then the whole tuple would be returned) - is it possible to combine the two arguments?

我想避免定义一个新函数并将其用作side_effect，我觉得在Mock中声明这两个函数更干净.

I want to avoid having to define a new function and using that as the side_effect, I feel having both declared in a Mock is cleaner.

推荐答案

答案为是否有可能使Mock对象在调用时返回值并在调用时执行语句?"显然是的，只需使side_effect做所有事情即可:

The answer to "is it possible to have a Mock object return a value when called as well as execute a statement when called?" is obviously yes, just make side_effect do everything:

import unittest.mock as mock

def side_effect():
      print('Side effect executed')
      return 'Returned Foo'

mocked_func = mock.Mock(side_effect=side_effect)

print(mocked_func())

# output
Side effect executed
Returned Foo

当然，您也可以使用lambda来做到这一点:

Of course you can do it with a lambda too:

import unittest.mock as mock

mocked_func = mock.Mock(
    side_effect=lambda: (print('Side effect executed'), 'Returned Foo')[1]
)

print(mocked_func())

# output
Side effect executed
Returned Foo

在我看来，它看起来并不干净，但对每个人来说却如此.如果您只是想避免污染名称空间，则可以执行以下操作:

It does not look any cleaner to me but to each their own. If you just want to avoid polluting your namespace you can do this:

def mocked_func():
    print('Side effect executed')
    return 'Returned Foo'
mocked_func = mock.Mock(side_effect=mocked_func)

或使用装饰器:

def mock_it(f):
    return mock.Mock(side_effect=f)

@mock_it
def mocked_func():
    print('Side effect executed')
    return 'Returned Foo'

像您已经注意到的那样，将return_value和side_effect合并似乎是不可能的.

Combining return_value and side_effect does not seem to be possible as you already noticed.

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