Debugging XSL can be a whole lot of fun. Hopefully, you've got an XML editor that allows you to run your transformation, which should help some, but if you run into problems once you've uploaded your module, it can be a bit of a pain to troubleshoot what's going on.
Help is here! You can use this form to run your transforms through our cleverly named Transformer (we like to think of it as a lawnmower that turns into a nerd). If it fails, you'll get a really disgusting java error, but it will hopefully lead you to your real problem.
One thing to keep in mind is the Transformer expects you to output valid XML from your transformations, which means you have to have a root element in your output. This one bit us, hence creating this form. Out of tragedy comes hope, right?