How do you test a relay if it is faulty or not?

Put a voltage(12V dc) across the coil terminals and see if it clicks. At the same time put a test light (battery operated) across the switched terminals and see if the light lights up. If if does, the relay is good. If it clicks and the light doesn't light up, the contacts are band. If it doesn't click, the coil is bad.

OR GO to any auto parts store, buy a new relay( about $2.00) and plug it in.