How do I test to see if my distributor is going bad?

why would you think its going bad? If you have good spark at the plugs then its good. Cap and rotor should be changed periodically but distributors are USUALLY good for life. The main thing that will go on a distributor depending on year, make and model, is the drive gear on the bottom. They are made softer than the cam gear so they wear faster. Some where even teflon/plastic and would wear out but the replacement gears where iron.

going bad ??? do you mean starting to fail misfire etc a banana goes bad rot etc .. going bad look in the english dictionary going bad HA HA you req to put it on a distributor test bench check dwell resistance kv etc