Another option is mentioned at http://jimfuller.blogspot.com/2007/09/poor-mans-unit-testing-with-xquery.html which is a kind of roll-your-own solution. I think that this may be the way to go, but I want to add a few more things:
- create the test methods on the basis on unit test best practice (if there is such a thing) this would involve some research to see if there is a meta-process for creating unit test systems - maybe xUnit will provide a template for this. I'm guessing a lot of this is premised on the testability of the harness itself (better watch out for a Gödel brick wall on this http://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorems)
- Make the functions more useful in a XQuery world, specifically being able to test if an XPath expression is true, this would allow me to test that a query result contains expected data - maybe this could be a set of expressions. This would be more powerful and flexible than just having "expected XML" output.
Anyway, some research first and then I can post up my first attempt (which will of course be pants)