Python从导入的模块中模拟函数

问题:Python从导入的模块中模拟函数

我想了解如何@patch从导入的模块执行功能。

这是我到目前为止的位置。

app / mocking.py:

from app.my_module import get_user_name

def test_method():
  return get_user_name()

if __name__ == "__main__":
  print "Starting Program..."
  test_method()

app / my_module / __ init__.py:

def get_user_name():
  return "Unmocked User"

测试/模拟测试.py:

import unittest
from app.mocking import test_method 

def mock_get_user():
  return "Mocked This Silly"

@patch('app.my_module.get_user_name')
class MockingTestTestCase(unittest.TestCase):

  def test_mock_stubs(self, mock_method):
    mock_method.return_value = 'Mocked This Silly')
    ret = test_method()
    self.assertEqual(ret, 'Mocked This Silly')

if __name__ == '__main__':
  unittest.main()

这不符合我的预期。“已修补”模块仅返回的未模拟值get_user_name。如何模拟要导入到被测命名空间中的其他包中的方法?

I want to understand how to @patch a function from an imported module.

This is where I am so far.

app/mocking.py:

from app.my_module import get_user_name

def test_method():
  return get_user_name()

if __name__ == "__main__":
  print "Starting Program..."
  test_method()

app/my_module/__init__.py:

def get_user_name():
  return "Unmocked User"

test/mock-test.py:

import unittest
from app.mocking import test_method 

def mock_get_user():
  return "Mocked This Silly"

@patch('app.my_module.get_user_name')
class MockingTestTestCase(unittest.TestCase):

  def test_mock_stubs(self, mock_method):
    mock_method.return_value = 'Mocked This Silly')
    ret = test_method()
    self.assertEqual(ret, 'Mocked This Silly')

if __name__ == '__main__':
  unittest.main()

This does not work as I would expect. The “patched” module simply returns the unmocked value of get_user_name. How do I mock methods from other packages that I am importing into a namespace under test?


回答 0

当您patchunittest.mock包中使用装饰器时,您未在修补命名空间,而是从(在这种情况下app.my_module.get_user_name)导入模块,而是在被测试的命名空间中对其进行修补app.mocking.get_user_name

为此,请Mock尝试以下类似方法:

from mock import patch
from app.mocking import test_method 

class MockingTestTestCase(unittest.TestCase):

    @patch('app.mocking.get_user_name')
    def test_mock_stubs(self, test_patch):
        test_patch.return_value = 'Mocked This Silly'
        ret = test_method()
        self.assertEqual(ret, 'Mocked This Silly')

标准库文档中包含一个有用的部分对此进行了描述。

When you are using the patch decorator from the unittest.mock package you are not patching the namespace the module is imported from (in this case app.my_module.get_user_name) you are patching it in the namespace under test app.mocking.get_user_name.

To do the above with Mock try something like the below:

from mock import patch
from app.mocking import test_method 

class MockingTestTestCase(unittest.TestCase):

    @patch('app.mocking.get_user_name')
    def test_mock_stubs(self, test_patch):
        test_patch.return_value = 'Mocked This Silly'
        ret = test_method()
        self.assertEqual(ret, 'Mocked This Silly')

The standard library documentation includes a useful section describing this.


回答 1

尽管Matti John的答案解决了您的问题(也为我提供了帮助,谢谢!),但是,我建议将本地的“ get_user_name”函数替换为模拟的函数。这将允许您控制何时替换功能以及何时不替换功能。同样,这将允许您在同一测试中进行多次替换。为此,请以类似的方式使用“ with”语句:

from mock import patch

class MockingTestTestCase(unittest.TestCase):

    def test_mock_stubs(self):
        with patch('app.mocking.get_user_name', return_value = 'Mocked This Silly'):
            ret = test_method()
            self.assertEqual(ret, 'Mocked This Silly')

While Matti John’s answer solves your issue (and helped me too, thanks!), I would, however, suggest localizing the replacement of the original ‘get_user_name’ function with the mocked one. This will allow you to control when the function is replaced and when it isn’t. Also, this will allow you to make several replacements in the same test. In order to do so, use the ‘with’ statment in a pretty simillar manner:

from mock import patch

class MockingTestTestCase(unittest.TestCase):

    def test_mock_stubs(self):
        with patch('app.mocking.get_user_name', return_value = 'Mocked This Silly'):
            ret = test_method()
            self.assertEqual(ret, 'Mocked This Silly')