A good ground. Or power. I usually run a wire from the battery to where I am working.

 

What type of wire ?
When testing the brake connector, am I testing for power , ground or both ?

 

Any wire. You are testing for both but since you only have one thing not working, I would say the ground is good. You are just missing power. If you don't have power you can split the harness. Up by the drivers side wheel (behind fender liner on the bottom of the cab) is a connector. Try to see if you have power there if you don't back at the brake light.

 

Finally checked my brake light.. It seems I don't have power going to the light/socket. Whats the quickest and easiest way to fix this ? Light being out is becoming a pain

 

Check for a broken wire somewhere.

 

Does the turn signal work?

 

No it doesn't . The other signals work fine

 

Just looking at your photos, the bottom socket looks like the prongs for the bulb might be missing or too wide/loose. This could also be a bad photo of the connector, but thought I'd mention it.

 

Do you know what the bottom socket is linked to ? Brake light, tail light, turn signal or reverse light ?

 

Not sure, but it looked like the metal bulb contacts were either non-existent or very wide, but that could have been the way the photo was taken. If you don't get good contact within the bulb socket, it certainly won't light up.