Sample usage of the `mock` module

gistfile1.sh

============================= test session starts =============================
platform win32 -- Python 2.7.6 -- pytest-2.5.1 -- D:\Programming\Python27\python.exe
plugins: xdist
collected 2 items

test_twitter.py:5: test_twitter PASSED
test_twitter.py:10: test_task_utils FAILED

================================== FAILURES ===================================
_______________________________ test_task_utils _______________________________

    def test_task_utils():
        with mock.patch('task_utils.mechanize_url') as mech:
            mech.return_value = 'MOCKED'
>           assert twitter.api() == 'MOCKED'
E           assert 'ORIGINAL' == 'MOCKED'
E             - ORIGINAL
E             + MOCKED

test_twitter.py:13: AssertionError
===================== 1 failed, 1 passed in 0.02 seconds ======================

task_utils.py

def mechanize_url():
    return 'ORIGINAL'  

test_twitter.py

import mock
import twitter
import task_utils

def test_twitter():
    with mock.patch('twitter.mechanize_url') as mech:
        mech.return_value = 'MOCKED'
        assert twitter.api() == 'MOCKED'

def test_task_utils():
    with mock.patch('task_utils.mechanize_url') as mech:
        mech.return_value = 'MOCKED'
        assert twitter.api() == 'MOCKED'         
            
  

twitter.py

from task_utils import mechanize_url

def api():
    return mechanize_url()  

Changing twitter.py to:

import task_utils

def api():
    return task_utils.mechanize_url()  

Causes test_twitter to fail and test_task_utils to pass:

============================= test session starts =============================
platform win32 -- Python 2.7.6 -- pytest-2.5.1 -- D:\Programming\Python27\python.exe
plugins: xdist
collected 2 items

test_twitter.py:5: test_twitter FAILED
test_twitter.py:10: test_task_utils PASSED

================================== FAILURES ===================================
________________________________ test_twitter _________________________________

Here is the version of the mock module I'm using:

>>> import mock
>>> mock.__version__
'1.0.1'