How to debug XSL Stylesheet in IS?

Can someone suggest, how to debug stylesheet (XSL) in IS?

We have Java services which calls XSL stylesheet and stylesheet has some conditional logic buit in it.

webMethods environment uses XSL file and it does not contain any tools like (XMLSPY or Altova) related to XSL stylesheet. So, wondering how can I test XSL stylesheet for testing and modifications.

Any suggestions please.