I'm doing Test First Challenge. William Wake has written a series of tests, the challenge is to write the code to pass those tests. At the end, you will have a simple spreadsheet program. I'm writing in Java, using IntelliJ IDEA and JUnit. I've succumbed to the power of the IDE (Integrated Development Environment), and unless Eclipse does something amazing, like actually work on my laptop for once, I'm staying with IntelliJ. Eclipse has the advantage of being free, but free isn't a lot of good when it goes with non-functional.
This test first stuff actually works. My own test first code is orders of magnitude cleaner than the old code, far easier to understand, and doesn't have tendrils all over the rest of the application. I'm stunned at the difference.