I always test the expo while I'm progeraming it. I test everything I program. It's too easy to get confused or make a mistake. I seem to make lots of those when I don't check everything. I can't imagine programing something without the RX on and then taking off without checking it.

To test expo while programing hold the stick between center and full(not centered, but not full throw) while changing the expo amount. The surface that you're controling should move closer to the center of the throw the more you add. If you're doing it backwards the surface will move away from center.