1990 ryder box van

Well I got the starter pulled out, while I was unbolting it from inside the cab through the doghouse access I glanced under the front seat and saw another starter laying there. I tested both of them on the ground using the van battery which I had charged up and no go. Took them both down to the parts store and they did the exact same test (using there machine) and they both tested perfect. Wtf? I'm guessing my battery is either weak, the cables iffy or I'm more incompetent than I realize. Anyways i'm going to test my battery and throw it back on the deep charger. Reinstall the starter, put in a new solenoid and both new battery cables. Cross my fingers and pray for a better result. Beyond that I don't know. I don't expect it to actually start right up as the guy said the ICM needs replacement. But it should at least turn over. Right?