I would try to build everything that is not directly related to the user interface in PORC (ordinary ordinary Ruby classes) and BDD, in the usual way require- later insert them into the boots. I suspect you are thinking of parts of the GUI, although I cannot help. All of the testing / behavior-related developments seem to be somewhat knocked down from the point of view of the GUI, Ruby is at least the same as any others, and the shoes are probably larger than most Ruby infrastructures.