It tells you in advance and you get a push to your phone if you're on the same network.

"This is a test. The alarm will sounds. The alarm is loud."

(or something like that)

I assumed you didn't get the push notification since your alarms weren't connected to the network properly.

Do you have a 1st gen? I wonder if they're louder. Mine (2nd gen) test pretty quietly. It's not the full-on alarm shriek. It a a medium-volume beeping and only happens for a couple of seconds.