Kriistinac

Battery light was on Monday, Tuesday I didn't drive it at all, Wednesday no light and started right up had defrost on high, had no power to windows or wipers. Try the wipers on fast speed and got a slow wipe out of them but caused heat to shut off. Turn it off and start back up an hour later, Drive for about a mile and dies. Jump start and starts right up, drives a few miles and got battery tested the guy said it was fine, drive for a few minutes then dies again, jump start again drives a few miles then dies going up a small incline. Any ideas? Should I just buy an alternator and have someone put it in?