I talked to one of the other devs, and it turns out I was making this too complicated. Trying to stub out the Ruby version and so forth would be a bit much. The behavior of testing the behavior on the given platform would be sufficient.

With respect to tests, we run the specs against 1.8.7, 1.9.3, and 2.0.0 on Travis-ci so this would be tested regardless, I was just a bit paranoid.