allow rake rails to run rails tests.
wait, i don't want that rails crap in my gemspec.
now this is fucking awesome. you can now do stuff as follows.

respond Group::Join::Leave do |op, format|
  format.html { redirect_to(user_groups_path, notice: op.message) }
  format.js   { head :no_content }
end

this calls respond_to internally and allows you to access formats: NO business logic in controller, only presentation!