Hi Shad,
Unfortunately, the Web Services testing feature does not support authentication at the moment. We have a corresponding suggestion in our database, and your request has increased its rating.
If you cannot disable authentication for the service, as a workaround, you can make use of the MSXMLHTTP object. However, in this case, you will have to prepare outgoing requests and parse responses manually in a script. You can find some information on this approach here:
http://www.sqaforums.com/showflat.php?Cat=0&Number=352016&page=0&fpart=all&vc=1&nt=2
