If you have a server that communicates with clients via XML messages, you can end up putting a lot of effort into using one of the unit-testing frameworks to test all the messages. Just think of all the code needed to set up communications, construct messages, and verify responses
A simple alternative is to document XML messages and expected responses, without having to write any code. Let XmlMessageTest send each XML message to the server, verify returned messages against expected results, and produce a simple report of test results.
XmlMessageTest is written in Java and should be able to run any Java-enabled platform. It's been tested on Windows XP and Linux. It can be easily integrated into your build process.