Saturn Ion alternator 2004 test and replacement

Car owner: hey, my battery light came on. Me: bad alternator, take it to a mechanic shop- don't delay (I didn't have time that day look at the problem). 3 days later at church- Me: what happened with the car? Car owner: the battery light went out so I kept driving. Me: Ok, perhaps it is not the alternator, possibly a loose connection. As I was about to leave the church parking lot- car owner: the battery light came on again. Me: Bring it over to me today, don't do any unnecessary driving. Later that afternoon... car owner: I'm about 2 min away. Me: Ok. Car owner: now my car wont start. Me: where are you? car owner: at the fasgas, I stopped to get fuel. Me: ....... Ok, be right there. Charged the battery enough to get it the next 2 blocks. Good Times! I am not in any way giving the owner a hard time. This is just an account of what happened. By Gods grace the car got close enough to me to take over.