How do i test the smoke alarms if only one goes off when you hit the test button.

Sounds like you're checking detectors wired in series..?

You need to break the Black and white wire apart and confirm that all alarms are on same power ckt, Then test that the red wire for interconnect in at each location. this can be tested also by continuty to the ground wire then at each location if temp connect it to ground at 1 location and test others , ( note : all units removed to test wiring)

No, the test is for each unit. Otherwise, if they all went off you wouldn't know which one was broken or needing a new battery. You go around the house and test each one and if it beeps, then you know its connected. You can always try covering the venting or putting some steaming water under the vent to set it off for real.