If you follow the Devise Wiki on setting up Rspec and Devise you may end up wanting to set an expecatation on the currently signed in user.
Don’t fall into the trap of setting it on the original user model as your specs will still fail:
user.should_receive(:blah).once # Won't work
Rather, you should set it on the controller’s current_user:
subject.current_user.should_receive(:blah).once # Will work!