I was really worried about thinking ahead about my XML format for id3v2test and then I realised that it's XML and it can be transformed with XSL into just about any other XML schema.

If I had 1000 tests in XML, I could update them all fairly easily. I wouldn't have to worry about not being able to refactor them becase XSL could be my refactoring mechanism.

How much of a pain would this be, though? It might be difficult if you don't know XSL that well, but at least your acceptance tests (and metadata) aren't locked into a vendor specific binary format, or worse: a specific programming language. You have a way out.