Yeah ZMAN is spot on.

With passive pickups at least (I don't have any active's to try this out on) you sure can do a basic test with a multimeter, measuring resistance between the top and bottom of each coil. If you look up the specs of the PU in question you'll likely even find what the resistance is supposed to be as well as the colour chart for the wires that'll make the testing a tiny bit easier.

Further testing is a bit rudimentary. Two suggestions I've read both involve wiring the PU directly into a guitar cord and into an live amp and then using a tuning fork waved over the PU or even lightly tapping the PU with something metal like a screwdriver (gasp).

If you -really- wanted to get hardcore though, I stumbled across THIS site. Caution. Engineering Content