I agree with TT_Mark, that you should only really test the browsers that your visitors use. From there you can create your priority list.
Senff pointed out a good tool to use if you’re on Windows. If you’re on a Mac then I think you can try out Adobe’s Browser Lab, but I’ve never used it so I’m not sure how good it is. The best way is to check the browsers out is by using a virtual machine. You don’t need to buy the expensive ones like VMWare or Parallels, there is a free one that is really good called Virtual Box.