If you suspect that your fog light switch is bad, the best way to diagnose it is by using a multimeter.  Set the multimeter to measure resistance, and then place one of its leads on the switch's terminal while the other lead is grounded.  If there is no change in resistance when you press the switch, this could indicate that there is an issue with the switch.  Additionally, if your fog lights don’t turn on when you push the switch, this could also be an indication that it’s broken or malfunctioning.