test a transmission out of the car?

I saw a video on Youtube where they hooked a drill to the input shaft and spun it while shifting the transmission through the gears and watched the tailshaft for movement.Is that possible to do or would it damage the transmission?

That must have been a HUGH drill for the chuck to open that far. Spinning the input shaft will do nothing, except tell if components are "welded" together. Spining the input shaft will not turn the front pump, and without oil pressure, nothing is going to engage.