The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
It depends on what you want to test. From a client perspective, to check that the pages are generating the correct content, HttpUnit might suit your needs. For unit testing JSP tags that you've built, TagUnit might give you something extra over just testing the tag handler classes with JUnit. For more complex in-container testing of Servlets and JSPs, try Cactus. For performance/stress testing, check out JMeter. Basically, there are lots of tools but it depends on what you want to do.