It appears the assumption is that the auto-feather will always work. If you don't experience a no auto-feather engine flame-out on takeoff scenario and you're curious maybe you can ask them to fly one as an extra. In the real world the system might be 99.999999% reliable, but one never knows.
The last place I worked testing the ATR AF was done on the taxi in on the last flight of the day, presumably avoiding maintenance from running it up, and if you guessed correctly, handing an airplane over with a fault to maintenance not at the start of the days flights. In that situation you could fly with a in-op AF system all day and not know it. Others probably do it differently, one hopes.