Make mock assertion failures readable

better_mock_error_messages.py

# mock objects print assertion failures in a way that is hard to read.
#
# Example:
#
# AssertionError: Expected call: <mock assertion failure: 1122331 ...>
# Actual call: <mock assertion failure: 112331 ...>
#
# After the patch:
#
# AssertionError:
# Expected call: <mock assertion failure: 1122331 ...>
# Actual call:   <mock assertion failure: 112331 ...>


import mock


# monkeypatch format_mock_failure_message so that expected and actual calls are actually aligned
# to make diff easier to read
def patched_format_mock_failure_message(self, args, kwargs):
    message = '\nExpected call: %s\nActual call:   %s'   # changed only this line
    expected_string = self._format_mock_call_signature(args, kwargs)
    call_args = self.call_args
    if len(call_args) == 3:
        call_args = call_args[1:]
    actual_string = self._format_mock_call_signature(*call_args)
    return message % (expected_string, actual_string)


mock.mock.NonCallableMock._format_mock_failure_message = patched_format_mock_failure_message  # pylint: disable=protected-access