TestXSLT is a small, AppleScript-able Cocoa application for experimenting with the XSLT and XSL-FO languages.

It uses the Sablotron, Gnome Libxslt, Saxon and Xalan-J XSLT processors, the FOP XSL-FO rendering engine, has lots of new features and a friendly user interface that makes playing around and learning XSLT fun.

Some features which were added recently like interactive well-formedness checking while you type or a tag completion feature also make it useful as a general-purpose XML editor.