Message 331433 - Python tracker (original) (raw)

It seems that TestCase in unittest.case accepts failureException attribute that is raised on assertion failure. My initial approach is to subclass TestCase and add a custom failure exception like MockException that is caught to add the diff to the original message. I am adding @cjw296 and @mariocj89 for feedback since I hope this can reuse unittest.case.TestCase implementation for diffs. I think this is better done with a flag like verbose=True to display the difference and defaulting to False since sometimes the message can be long depending on args and kwargs. Also I find args (tuple) comparison to be little distracting. Since this is an enhancement I am adding 3.8.

Sample file

from unittest.mock import Mock

m = Mock() m(1, 2, foo='bar', bar='baz') m.assert_called_with(2, 3, bar='baz', foo='car')

On 3.7

$ python3.7 /tmp/foo_4.py Traceback (most recent call last): File "/tmp/foo_4.py", line 5, in m.assert_called_with(2, 3, bar='baz', foo='car') File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/unittest/mock.py", line 820, in assert_called_with raise AssertionError(_error_message()) from cause AssertionError: Expected call: mock(2, 3, bar='baz', foo='car')

With patch

$ ./python.exe /tmp/foo_4.py Traceback (most recent call last): File "/tmp/foo_4.py", line 5, in m.assert_called_with(2, 3, bar='baz', foo='car') File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/unittest/mock.py", line 844, in assert_called_with raise AssertionError(_error_message()) from cause AssertionError: Expected call: mock(2, 3, bar='baz', foo='car') Actual call: mock(1, 2, bar='baz', foo='bar') args: Tuples differ: (2, 3) != (1, 2)

First differing element 0: 2 1