I haven't done nearly enough to thank Pat Eyler for all his great work writing about ZenTest. He's done an awesome job of getting the word out there about ZenTest (and pretty much everything else we do). Here is some of the stuff he's written:
Welcome to The Gemcutter's Workshop covers ZenTest, unit_diff, and autotest along with a plethora of other great testing and development tools.
How to Use ZenTest with Ruby - included with ZenTest - covers refactoring and unit testing in the more traditional (non-TDD sense).
Test-first Ruby programming (requires login) - shows how to use ZenTest with in a test-first environment.
Again... thanks Pat!
flatterer.