Python Mocking a function from an imported module

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?

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.

From: stackoverflow.com/q/16134281

Back to homepage or read more recommendations: