Jeep Cherokee intermittent charging problem?

I had the same exact car, same exact problem with that GEN light...changed the alternator and serpentine belt, and it worked like a charm. I actually think it was the bearing in the pulley on the alternator, because when the alternator was failing, it squeaked like a beast. So the alternator itself may charge ok, but the bearing in the pulley isn't spinning correctly. I don't know how accurate bench testers are for alternators but it could be also like the other guy said that the alternator is failing intermittently.