I've read a little bit about Cucumber: "Behavior Driven Development with elegance and joy". ( Behavior Driven Development = BDD )
Sounds cool! As I get my hands into it a little bit, it almost feels like "pre-testing", and it fits well into how I've been developing for years, i.e. developing on the fly, a.k.a. agile development.
I'm not sure if other Ruby developers who use Cucumber consider it having anything to do with testing, but that's how I see it at this point.
As I get further into Ruby, the wide range of testing tools is amazing me: