> We built a query that compares two sets of data by simply doing a count of the table and a count of the union. If they're different, it fails the test. Simplistic and limited it may be, but it gets the job done. We had tried exporting data to XML & doing all kinds of other comparisons, but this simple approach seemed to work much better than the fancier ones.

I did that at first, but found that unit tests failed more frequently than taking a known bit of data that hasn't changed in a long while, and using that instead.