Demo-harmony is a project mainly written in Ruby, it's free.
Demonstration of using Harmony (Johnson+EnvJS) with Cucumber
You should do the following for some fun times.
$ gem install stackdeck
$ gem install envjs
$ gem install johnson -v "2.0.0.pre3"
$ gem install harmony
$ gem install cucumber
$ cucumber
Then you get something neat like this:
Enjoy the awesome.