It’s easy enough to do but a pain to describe….
There are tutorials on the RSpec site (looks like that’s the package your using).
Also take a look on the Visual Spec site (http://astrosurf.com/vdesnoux/) , there’s a comprehensive tutorial using Vega. That’s the technique I use. I much prefer working with Visual Spec and IRIS. They don’t have the slick interface but I like the command line method, makes you think about what your doing.