He is talking about an IDE feature that indicates that, well, your test passed!
http://www.eclipse.org/ajdt/EclipseCon2006/shots/junitTestsP...
The idea is that you write a few lines of code, test it (most likely you'll get red), and you keep fixing your code until you get green, and only then you proceed to the next task.
As far as I know, it started with jUnit on Eclipse, and then others implemented the concept on other languages / IDEs.