Wow. My humor is pretty crude but I'd never made the connection to testicles before. I'd just assumed it was a portmanteau of "test" and "spectacular" but I am British and the latter word still sees some usage ;-)
As an American it took... perhaps 5 minutes or so to scratch my head at the name :).
Very cool project. Nothing like having your tests run every time you save a file... in several different browsers if you like. This and docco made me think about about node differently. Though it is a server side JavaScript framework, it has also become a platform for developer automation tasks.
I believe one of the guys behind this is Misko Hevery (of AngularJS). He's test-driven mad (which is a good thing IMO). I've been meaning to try Testacular / Karma out just because of the pedigree.
Autorunning tests is cool, and great for TDD. I usually just use Guard for that, but I can understand why they would build their own thing to suit their needs better.