Somehow I doubt that his existing code has unit test
code with it. So just what is it supposed to do? Mudding
the difference between what it's defined to do vs what it
just happens to do is one of my pet issues, too.
In this case, I'd probably try to test against what the
old code actually does, especially if it's been in
production for a while (with people depending on its
quirks). Exercise each feature of the old code (and any
combinations that seem to be interdependent), capture the
output, and diff. (Not nearly as easily done as said, I
know. :-( )
The hell with paco, vote for Erudil!