Yep, that test works and yep, it will read 0 (instead of ---) so you will KNOW it is working before installing. Nothing fancy needed through- just use a piece of string, tie it to the stem of the sensor and swing it around like a 1930's gangster movie star would. Works great.
This one time, at band camp, I changed the batteries on this gentleman's bike.... both sensors at once so I cleverly marked the sensors with an "F" and an "R". Slick, huh? Yep..... then I took the sensors apart and mixed up which internal parts (Easy Boys!) came from which sensor case. Yeah, maybe not so clever after all. :-) So I did the string swing thingie and it worked great. Put the sensors back in the bike, bid the gentleman good day and as soon as he was down the driveway I ran away as fast as I could. This leaves me pleasantly confident that his sensors both worked then as well as still.
But really, just swing the sensor around by the stem and it will work. It takes about 30 seconds to register with the bike though so be a bit patient.
Brian
At my last tire change I changed the battery on the front TPMS and it hasn't worked since. Haven't had time to pull the tire again to fix it. So next time I was thinking of making kind of a sling with the unit properly orientated and spinning it around. Was hoping if it worked that instead of -- it might show 0. Would like to know if it is working or not before mounting the tire.