python mock assert_called_with

Question

I'm trying to understand the assert_called_with within mock but the code I wrote throws some error.

import os
import twitter

URL = "http://test.com"

def tweet(api, message):
    if len(message) > 40:
        message = message.strip("?.,.,.")

    status = api.PostUpdate(message)
    return status

def main():
    api = twitter.Api(consumer_key=''
                    ,consumer_secret='')
    msg = 'This is test message'
    tweet(api, msg)

if __name__ == '__main__':
    main()

unittest

import unittest
from mock import Mock
import test

class TweetTest(unittest.TestCase):
    def test_example(self):
        mock_twitter = Mock()        
        test.tweet(mock_twitter,'msg')        
        mock_twitter.PostUpdate.assert_called_with('message')        

if __name__ == '__main__':
    unittest.main()

I'm trying to understand what assert_called_with does here?

Solution

According to the python documentation https://docs.python.org/3/library/unittest.mock.html#unittest.mock.Mock.assert_called_with

'This method is a convenient way of asserting that calls are made in a particular way'

so it tests whether the parameters are being used in the correct way.

About the errors that you are receiving, I think the parameter you're passing is wrong. Its have to be something like this:

mock_twitter.PostUpdate.assert_called_with(message='msg')