How do I mock methods of global object in python?

Question

I have a file say twitter.py in which I have two global objects: user and tweet. I have another file say twitter_utils.py in which I have imported module twitter and have written few methods using global objects as following:

twitter_utils.py:

import twitter

def __get_user_date_of_birth(user_id):
    return twitter.user.get_date_of_birth(userId=user_id)

def __get_tweet_likes_count(user_id, tweet_id):
    return twitter.tweet.getLikesCount(user_id, tweet_id)

I created a file test_twitter_utils.py and tried writing tests for above methods. Following is an attempt:

import twitter
import twitter_utils

@patch('twitter_utils.twitter.user')
def test_get_user_date_of_birth(mock_user):
    mock_get_date_of_birth = Mock(
            return_value='18 Aug 1989')
    mock_user.attach_mock(mock_get_date_of_birth,
                                          'get_date_of_birth')
    twitter_utils.__get_user_date_of_birth('test')
    assert mock_user.mock_get_date_of_birth.call_count == 1

Above test fails with an assertion error saying, assert 0 == 1. Essentially saying that mock_user.mock_get_date_of_birth.call_count = 0. What am I doing wrong ? Am I importing things in wrong fashion ?

Answer 1

I believe you need to mock using the path that your module imports. twitter_utils.py imports twitter , so your patch should be patching twitter .

@patch('twitter_utils.twitter') .

You can then mock functions from there.

Had you been doing an import like:

from twitter import user as twitter_user

Then your patch would be @patch("twitter_utils.twitter_user")

Also, not sure if you are aware, but when writing tests it's good to use unittest framework. https://docs.python.org/2/library/unittest.html