How to patch a module's internal functions with mock?

Question

By \"internal function\", I mean a function that is called from within the same module it is defined in.

I am using the mock library, specifically the patch decorators,

Answer 1

The answer: Clean up your darned imports

@patch('mymodule.TAX_LOCATION', '') did indeed patch things appropriately, but since our imports at the time were very haphazard -- sometimes we imported mymodule.build_cart, sometimes we imported project.mymodule.build_cart -- instances of the "full" import were not patched at all. Mock couldn't be expected to know about the two separate import paths... without being told explicitly, anyway.

We've since standardized all our imports on the longer path, and things behave much more nicely now.

Answer 2

I'm pretty sure your problem is that you are importing 'mymodule' inside your test functions, and therefore the patch decorator has no chance of actually patching. Do the import at the top of the module, like any other import.

Answer 3

I'd like to add solution other than accepted one. You can also patch the module before it's been imported in any other modules and remove patch at the end of your test case.

#import some modules that don't use module you are going to patch
import unittest
from mock import patch
import json
import logging
...


patcher = patch('some.module.path.function', lambda x: x)
patcher.start()

import some.module.path

class ViewGetTests(unittest.TestCase):

  @classmethod
  def tearDownClass(cls):
      patcher.stop()

Answer 4

another option is to explicitly call patch on the function:

mock.patch('function_name')

and to support both running directly or from py.test etc:

mock.patch(__name__ + '.' + 'function_name')