There's some really expensive packages out there for automated website testing. These things cost thousands of dollars, usually only run on windows, and are huge bloated software packages. There great for your average QA person to quickly "record" a web session and play it back later.

But developers have different needs than QA folk, and we'd like to do automated tests as well. My requirements are as follows:

1) Cross platform (windows, osx, linux, more is nice)
2) Allows me to simulate all types of requests to a web server / service.
3) Can be integrated into ant for completely hands-off testing.
4) Can verify any element of a page.

The package I've been using for this is called Hatatap.

It allows you to construct o-xml programs that easily fulfill all of my requirements. o-xml is an object orientated programing language that's written entirely in XML. If you have a good XML editor that understands XML schemas, than you get all the nice context sensitive completion you expect from a modern development environment.