Battery light will not turn off

I came home just before the driveway truck power shutdown; truck was still running. shut off the ignition and truck try to start no go, I changed the alternator with brand new one, then a new battery was put in. battery light still on. I charged battery still no good. went had alternator and the battery tested both were running as it should brand new, but the light won't go off. I tried letting it sit for 8 hours still won't go off. I've checked connections, had both tested and still no idea how to get that battery light off.