If the tester bulb lights, power is still flowing to the switch.

If he votes "Yes", a green bulb lights up alongside his name on the scoreboard in the front of the chamber.

If the test bulb lights, power is still reaching the receptacle.

If the test bulb lights, power reaches the fixture.

If the bulb lights at any time, do not proceed until you can turn off the power.

If the test bulb lights, the power is getting as far as the fixture.

If the bulb lights brightly, the box is grounded.

You close the switch and the bulb lights up.

Paul laughed when he saw my bulb light up.

If the bulb lights at any time, the power is still on and must be shut off before you proceed.