[英]How to mock imported library methods with unittest.mock in Python 3.5?
Is it possible to mock methods of imported modules with unittest.mock in Python 3.5?是否可以在 Python 3.5 中使用 unittest.mock 模拟导入模块的方法?
# file my_function.py
import os
my_function():
# do something with os, e.g call os.listdir
return os.listdir(os.getcwd())
# file test_my_function.py
test_my_function():
os = MagickMock()
os.listdir = MagickMock(side_effect=["a", "b"])
self.assertEqual("a", my_function())
I expected that the the os.listdir method returns the specified side_effect "a" on the first call, but inside of my_function the unpatched os.listdir is called.我希望 os.listdir 方法在第一次调用时返回指定的 side_effect "a",但在 my_function 内部调用了未修补的 os.listdir。
unittest.mock
have two main duties: unittest.mock
有两个主要职责:
Mock
objects: object designed to follow your screenplay and record every access to your mocked object定义Mock
对象:旨在遵循您的剧本并记录对Mock
对象的每次访问的对象In your example, you need both functionalities: Patching os.listdir
reference used in production code by a mock where you can have complete control of how it will respond.在您的示例中,您需要两种功能: 修补生产代码中使用的模拟os.listdir
引用,您可以在其中完全控制它的响应方式。 There are a lot of ways to use patch
, some details to take care on how use it and cavelets to know .有很多方法可以使用patch
,一些细节需要注意如何使用它以及要知道的小窝。
In your case you need to test my_function()
behaviour and you need to patch both os.listdir()
and os.getcwd()
.在您的情况下,您需要测试my_function()
行为,并且需要修补os.listdir()
和os.getcwd()
。 Moreover what you need is control the return_value
(take a look to the pointed documentation for return_value
and side_effect
differences).此外,您需要的是控制return_value
(查看有关return_value
和side_effect
差异的有针对性的文档)。
I rewrote your example a little bit to make it more complete and clear:我稍微重写了你的例子,使其更完整和清晰:
my_function(nr=0):
l = os.listdir(os.getcwd())
l.sort()
return l[nr]
@patch("os.getcwd")
@patch("os.listdir", return_value=["a","b"])
def test_my_function(mock_ld, mock_g):
self.assertEqual("a", my_function(0))
mock_ld.assert_called_with(mock_g.return_value)
self.assertEqual("a", my_function())
self.assertEqual("b", my_function(1))
with self.assertRaises(IndexError):
my_function(3)
I used the decorator syntax because I consider it the cleaner way to do it;我使用装饰器语法是因为我认为它是一种更简洁的方法; moreover, to avoid the introduction of too many details I didn't use autospecing that I consider a very best practice.此外,为了避免引入太多细节,我没有使用我认为是最佳实践的自动指定。
Last note: mocking is a powerful tool but use it and not abuse of it, patch just you need to patch and nothing more.最后一点:mocking 是一个强大的工具,但请使用它而不是滥用它,修补只是你需要修补而已,仅此而已。
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