Testing propane alarm in more life like conditions?

Butane test sounds good for actual function- any bic/flick type lighter would do the trick. But if it's "real life" conditions you want to test for, I don't see any better than the one you already propose: turn gas on, shut door, and wait for the alarm. The timing would certainly be interesting...

But do make sure you've shut everything else in the vicinity down first, and stand there with your hand on the tank shutoff valve!