I have 92 subaru legacy while I am driving the battery light will come on and go off and my battery will eventualy die and the car will die when im at ideal and I have to jump it to get it going again. I had the charging system tested and it was good

Have your mechanic check ALL of the wiring. Something could be shorting out. Also, clean the contacts of your battery. And with electrical problems, you can never rule out the alternator. Especially if it's not charging properly.

i think it the voltage regulator which, on that car, is located inside your alternator on the back side. If you are capable of rebuilding your own alternator i would recommend doing so. that way you dont have to buy a new one for 150 dollars or a used one for 60 dollars that cant be guaranteed. dont call a napa or shucks store for your parts because they will charge you just as much for those parts as they would for a whole new alternator. call a local alternator rebuild shop and tell them you need a new voltage regulator and brush holder they should charge you about 40 bucks. if you dont have the time to do it yourself then i would definitely go out and buy a new alternator, because thats your problem.