Python Mock getting address instead return_value

Question

I am trying to sub out a call to check a users full name. I have written the below method using mock to do this.

def test_UserDisplayName(self):
    appModel = Mock()
    eval = appModel.eval.return_value
    eval.userDisplayName.return_value = 'JohnDoe'
    self._SummaryModel.AppModel = appModel
    actual = self._SummaryModel.UserDisplayName()
    self.assertEqual(actual, 'JohnDoe')

This is the method it is calling.

def UserDisplayName(self):
    return self.AppModel().eval().userDisplayName()

If I attached debugger to the above line and the run it in the shell it works

[PAUSED] >>> self.AppModel().eval().userDisplayName()
'JohnDoe'
[PAUSED] >>> 

But when the run the test case for it fails as it I am getting the address back rather than the value.

   ======================================================================
   FAIL: test_UserDisplayName (unittests.model.SummaryModelTest)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "/unittests/summary_model.py", line 112, in test_UserDisplayName
       self.assertEqual(actual, 'JohnDoe')
   AssertionError: <Mock name='mock.userDisplayName()' id='233406864'> != 'JohnDoe'

   ----------------------------------------------------------------------
   Ran 1 test in 0.010s

   FAILED:  (failures=1)

What am I doing wrong?

Answer 1

Your code calls AppModel as well, so you need to adjust the other references for that:

eval = appModel.return_value.eval.return_value

Demo:

>>> from unittest.mock import Mock
>>> appModel = Mock()
>>> eval = appModel.return_value.eval.return_value
>>> eval.userDisplayName.return_value = 'JohnDoe'
>>> appModel().eval().userDisplayName()
'JohnDoe'

However, your <Mock name='mock.userDisplayName()' id='233406864'> object shows a name of mock.userDisplayName() which suggests that the return value was produced by using self.AppModel.userDisplayName() directly instead.