Sun Equipment offered a bench tester for starters, alternators, generators and voltage regulators but it was large, heavy and required several batteries plus 220v power. I sold one to the federal government after I diagnosed the problem they were having with Dodge trucks not charging. They had a shelf full of new voltage regulators that were bad out of the box and trucks with corroded bodies and large alternator pulleys on engines that idled most of the time with all accessories running. A man named Messerschmidt was the purchasing agent for the Air Force base, believe it or not.