Debug XSL (XML Transformations)

Firebug, a fantastic FireFox extension for client-side debugging of DOM Scripting, does not support XML/XSL debugging. This is unfortunate, since it's free and it seems like something almost every developer already has installed.

Microsoft Visual Studio sports an XSLT debugger, but only if you have the Professional or Team Edition; it is not available in the freeware Express versions or Standard.

Stylus Studio's XSLT Debugger is a fantastic full-featured IDE for stepping through XML transformations, but at $99 bucks it ain't quite under my painful payment threshold. There's even a "professional" version which is magnitudes more expensive, but the standard one worked fine for me when I tried it for a trial period. The one thing I could not figure out how to do for the life of me was edit a pre-existing "scenario" (e.g. what XML to load for a particular XSL), even though I did find how to add new ones. Very strange.

Lastly, you can use <xsl:message /> for simple tracing, but it only works in FireFox and Mozilla's XSL support has some holes.