85 Suburban won't crank

Hi.. I've got an 85 suburban that runs a little rough but has always started until yesterday that is. Drove to the store and came back out, wouldn't crank.

Had it towed home checked that battery it's fine. I have juice down to the big post on the starter, and juice on the smaller post when the key is turned. Tried jumping across directly but doesn't kick at all.

Took the starter over to autozone and when they hooked it up, it engaged no problem. I brought it back and put it back on but nothing.

Don't know where to go from here. Maybe it is the starter since I can't get it to turn even when i bypass the switch?

i think you have bad starter