Agreed. An ohmmeter will verify a circuit through the coil, but it can't tell you if the mic has had a knock and the coil is jammed etc. Easiest way by far is to plug into a known good amp.
Use caution if the amplifier is old or of questionable condition. Be sure you're not grounded in case there is a chassis leakage problem!!
Ah.... On the subject of the "finger-injected" test signal that reminds me of this one:
Famous Last Words #249:
"Of course the top cap is the grid."
