How to check rear fog wiring?
 

My left rear fog light doesn't work. I know for sure that the bulb and the socket (see attahced images) work. I switched between left and rigth lights to check.
How do I check the wiring? Can I first of all check the voltage just by sticking the multimeter inside the socket? If yes and it shows 0 voltage, what should I check next?
https://cimg2.ibsrv.net/gimg/minicoo...0fb4f6b645.jpg
https://cimg3.ibsrv.net/gimg/minicoo...002bd40352.png