How to test alternator

positive in the well and negative on the side of the well. or you could just open the hood and test at the battery on pos and negative terminals. Then crank the car and check again. 12.5+ shut off and 13+ while idling should be a good. any less and you should be looking at either the alternator or the battery accordingly. At least that's the check i do every day up at the good ole autozone i work at.