2003 Chevy 2500 express van

2003 Chevy 2500 Express VanHad a problem that van would crank intermittently, the problem had grown worse. I replaced the starter relay and problem was still there so I pulled the starter and had it tested (it was fine) I reinstalled the starter and when I connect the battery the starter spins without the key being turned. I replaced the ignition switch and the problem is still there. No matter what I do, once I connect the battery the starter spins on its own.