You can't performance tune without some testing of how efficient things are. I guess I was wondering as well whether people actually think about testing beyond that. Jeff addressed some of that in his first comment, but most others haven't.

Do you look for edge cases? In other programming, you can send in zeros, too much data in a parameter, etc., but do you do that in SQL?

For example, do you look at aggregations with and without NULLs in there? Do you examine what happens for character comparisons if you have numerics or dates in the fields? Do you look for implicit conversions that could cause issues?

Those are more what I think of when I consider unit tests. My feeling is that most developers aren't overly concerned with more than getting back the correct result set with their test data.