Patch over a function imported inside another function

In order to avoid a circular import, I've been forced to define a function that looks like:

# do_something.py def do_it(): from .helpers import do_it_helper # do stuff 

Now I'd like to be able to test this function, with do_it_helper patched over. If the import were a top level import,

class Test_do_it(unittest.TestCase): def test_do_it(self): with patch('do_something.do_it_helper') as helper_mock: helper_mock.return_value = 12 # test things 

would work fine. However, the code above gives me:

AttributeError: <module 'do_something'> does not have the attribute 'do_it_helper' 

On a whim, I also tried changing the patch statement to:

with patch('do_something.do_it.do_it_helper') as helper_mock: 

But that produced a similar error. Is there any way to mock this function, given the fact that I'm forced into importing it within the function where it's used?

1 Answer

You should mock out helpers.do_it_helper:

class Test_do_it(unittest.TestCase): def test_do_it(self): with patch('helpers.do_it_helper') as helper_mock: helper_mock.return_value = 12 # test things 

Here's an example using mock on os.getcwd():

import unittest from mock import patch def get_cwd(): from os import getcwd return getcwd() class MyTestCase(unittest.TestCase): @patch('os.getcwd') def test_mocked(self, mock_function): mock_function.return_value = 'test' self.assertEqual(get_cwd(), 'test') 

Hope that helps.