Re: starter question
The trouble with a part's store test is they just put poweer to it - if it spins it's OK. It's not under load, so even defective most will pin.
The best way to test off the car is with a carbon pile load in series with the battery. Screw the load down tight - least resistance. Get it spinning, then slowly increase the carbon pile's resistance - it'll slow down. You should be able to make it go really slow. If there's a bad segment it'll stall at that point. You can "help" it past that point but it'll stall next time around.
Parts store kids don't know how to do that.
Actually the best way to test is on the car, with it's normal cables and battery. You want a minimum of 120 RPM cranking speed and calculate 2/3 of the CU" displacement in amps.
Fir instance a 300 cu" engine should not exceed 200 Amps. Preferably less than 1/2 or 150 in the example.
Measure along the length of each cable too - maximum voltage drop for each cable is .5 volts DURING CRANKING, preferably MUCH less.
Battery should have at least 9.6 volts while still cranking after 15 - 20 seconds of cranking too.