On 12/20/2010 6:31 AM, Antoine Pitrou wrote:
> Diffing is completely an implementation detail of how the failure 
> messages are generated. The important thing is that failure messages 
> make sense with respect to actual result and expected result.
Which, again, they don't. Let's see:

    self.assertEqual(actual, expected)
AssertionError: 'a\nb\nc\ne\n' != 'a\nb\nc\nd\n'
- e
+ d

The diff shows "expected - actual", but it would be logical (in your own
logic) to display "actual - expected". The whole issue disappears if you
drop this idea of naming the arguments "actual" and "expected".

I'm not a unittest user, although I probably will become one, in time, when I learn enough to contribute to Python, instead of just find bugs in it from use.

I don't much care what the parameters names are, although the terms actual and expected seem good for testing scenarios if properly used, but the above does not match what I would expect the behavior to be from a testing scenario: run the test, and tell me what changed from the expected results.

If the expected result (not parameter) is d and the actual result (not parameter) is e, the diff should show

- d
+ e

Thinking-that-sometimes-a-novice's-expectations-are-relevant-to-such-discussions'ly yours,