ZenTest provides 3 different tools: zentest, unit_diff, and autotest. ZenTest scans your target and unit-test code and writes your missing code based on simple naming rules, enabling XP at a much quicker pace. ZenTest only works with Ruby and Test::Unit. unit_diff is a command-line filter to diff expected results from actual results and allow you to quickly see exactly what is wrong. autotest is a continous testing facility meant to be used during development. As soon as you save a file, autotest will run the corresponding dependent tests. There are two strategies intended for ZenTest: test conformance auditing and rapid XP. For auditing, ZenTest provides an excellent means of finding methods that have slipped through the testing process. I've run it against my own software and found I missed a lot in a well tested package. Writing those tests found 4 bugs I had no idea existed. ZenTest can also be used to evaluate generated code and execute your tests, allowing for very rapid development of both tests and implementation.