Unable to mock a function in Python (Django)

Question

I'm trying to mock a function used within the function I'm testing, but for some reason I'm not seeing the original function always runs, not the one I created as a mock.

The code I'm testing has this type of setup:

def function_being_tested(foo):
    ...
    function_i_want_to_mock(bar)
    ...

def function_i_want_to_mock(bar)
    print("Inside original function")
    ...

I've installed Mock and I've tried using unittest.mock patch

Currently the test file uses this setup:

import mock
from django.test import TestCase


def mock_function_i_want_to_mock(bar):
    print(bar)
    return True


class SupportFunctionsTestCases(TestCase):

    @mock.patch("path.to.function.function_i_want_to_mock", mock_function_i_want_to_mock)
    def test_function_being_tested(self):
        # setup
        result = function_being_tested(test_foo)
        self.assertEqual(result, expected_result)

What then happens is when I run the test, I always get: "Inside original function", not the parameter printed so it's always running the original function.

I've used this exact setup before and it has worked so I'm not sure what's causing this. Probably some wrong setup...

If anyone has a different way of doing this or spots some error, it would be appreciated.

Dušan Maďar · Accepted Answer · 2024-06-20 19:20:10Z

16

"path.to.function.function_i_want_to_mock" should be a path to where the function is used, not defined.

So if function_i_want_to_mock is defined in module_A.py but imported and used in module_B.py, which you are testing, then you should use @mock.patch("path.to.module_B.function_i_want_to_mock", ...).

edited Jun 20, 2024 at 19:20

answered Feb 8, 2018 at 10:23

Dušan Maďar

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2 Comments

steinarey Over a year ago

This solved it! In my previous usage of this the inner functions I was testing were in the same module as those I was mocking so this discrepancy was "hidden" to me. Thank you!

Ron Over a year ago

Oh my god, you saved my life! ❤

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