Unit Test Problem with assertRaises

Question

I am trying to test for an exception.

I have:

def test_set_catch_status_exception(self):
    mro = self.mro
    NEW_STATUS = 'No such status'
    self.assertRaises(ValueError,mro.setStatus(NEW_STATUS))

I get the following error:

======================================================================
ERROR: test_set_catch_status_exception (__main__.TestManagementReviewGoalGetters)
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Traceback (most recent call last):
  File "test_ManagementReviewObjective.py", line 68, in test_set_catch_status_exception
    self.assertRaises(ValueError,mro.setStatus(NEW_STATUS))
  File "/Users/eric/Dropbox/ManagementReview.py", line 277, in setStatus
    raise ValueError('%s is not in the list of allowed statuses: %s' % (status,LIST_OF_STATUSES))
ValueError: No such status is not in the list of allowed statuses: ['Concern or Delay', 'On Track', 'Off Track/Needs Attention']

----------------------------------------------------------------------

Thanks

Answer 1

self.assertRaises expects a function mro.setStatus, followed by an arbitrary number of arguments: in this case, just NEW_STATUS. self.assertRaises assembles its arguments into the function call mro.setStatus(NEW_STATUS) inside a try...except block, thus catching and recording the ValueError if it occurs.

Passing mro.setStatus(NEW_STATUS) as an argument to self.assertRaises causes the ValueError to occur before self.assertRaises can trap it.

So the fix is to change the parentheses to a comma:

self.assertRaises(ValueError,mro.setStatus,NEW_STATUS)