Absolutely fantastic:
The Poka-Yoke principle and how to write better software
Basic Tenents of Poka-Yoke Testing:
- Unit Tests have to be as fast as lightning
- Quick and slow tests should be separated
- Tests must be reliable
- Tests must be repeatable
This is the gist of what I try to teach coming on to any new project. Beautifully written. I'll have to steal some of the language simply because it gets the point across so well.

It's funny reading this because I'm waiting for unit tests to run...about 5 minutes down, another 5 to go...