Well, as an electrical engineer with more than 30 years experience, I am quit familiar with a voltage drop test. It's a very good test, where it's needed.
For quick troubleshooting, a test light and a DMM will tell you a lot, quickly and easily. If that isn't enough, a voltage drop test just might be the ticket. Of course, you have to have access to both ends of the circuit under test, which isn't always the case, and you have to know the circuit, and you have to be able to load the circuit.
Many times, a test light does it. Simple.