Pavel Sher has posted Juxy 0.6.5, "a simple unit testing library for XSLT written in Java. Juxy allows to call or apply individual XSLT templates from Java and does not use any specific features of XSLT processor for that purposes. It relies entirely on TRaX API and should work with any TRaX compliant XSLT processor." A quick glance at the examples makjes it look really ugly. The integration with Java seems ot be the main problem.
By contrast, Jeni Tennison has released a set of stylesheets that are designed to support unit testing of XSLT stylesheets. In other words this tests XSLT with XSLT. That seems much more natural. On the other hand, it requires XSLT 2.0 which Jaxy doesn't. A batch file is provided that runs the tests with Java. However, any XSLT 2.0 processor should do the trick. According to Tennison, "You embed tests in the stylesheet and can run a script (or configure your editing environment) to extract and run them and create an HTML report on the result." Saxon 8.4 is required to run the .bat file. (No Unix or Mac support yet, though.)