This question is an old one, but it shows up at the top of Google when searching for how to run a single test. I don't know if it's a recent addition, but to run a single test out of a spec you can do the following:
rspec path/to/spec:<line number>
where -line number- is a line number that contains part of your test. For example, if you had a spec like:
1:
2: it "should be awesome" do
3: foo = 3
4: foo.should eq(3)
5: end
6:
Let's say it's saved in spec/models/foo_spec.rb. Then you would run:
rspec spec/models/foo_spec.rb:2
and it would just run that one spec. In fact, that number could be anything from 2 to 5.
Hope this helps!