a voltage drop test is done point to point along a complete circuit. The idea is to not see more than .2 volts on non-electronic circuits. You are measuring the loss of voltage along a path which indicates a poor connection. Much more accurate the an ohmmeter test and usually much easier and quicker to do

check out this video for good example of how to do a voltage drop test

for a more in depth understanding here is another great resource




Let me know if anyone finds this useful