Testing Starter

I have had success using the following method.Now, I warn you its not very scientific, but it will tell you what you need to know. When its 30 below outside, where your car is, even just bolting the starter up is a chore I dont relish.
So this was my test rig.
I clamped the starter HARD in a big vise, on a very heavy bench,by one of its ears.I connected a battery up to it using generous sized cables and clamps. I hooked my remote starter button up, so it was ready to spin up.
I then took a 2x2x24 stick of wood and jammed it on the drive and under/against the vise body, in such a way that I could put my body weight on that stick in an attempt to stall the drive.
Then with the remote in one hand, and the stick in the other, I went to it.As the starter speed came up, I tried to stall the motor out with the stick. It made a lot of noise, and the stick took a licking, but a bad starter showed up instantly.

BTW, at that time, I had near 2 dozen starters.I discovered that there were several different types of Chrysler starters in at least two different cases.Not all of those old starters were the same,even though they may look similar or even the same.
I rebuilt/reconditioned about 4,or 5, or 6 of them,IDK. That was in the late 90s or so.I think I may still have 1 or 2 left. I dont use those any more, now since the mini came to market.