Digital multi-meters have come a long way since I first used them. Back then all they gave you was voltage, current and resistance. My new DMM also has a temperature probe, measures capacitance and tests diodes and transistors.
During the process of sacrificing and dissecting a couple of old laptop power bricks, I've harvested a number of components, including transformers, inductors and capacitors.
Testing a capacitor to see if it's still good is pretty simple by checking the resistance. Low resistance is bad, very high/infinite resistance is good, high but not very high is leaky.
I'd also like to know what the actual capacitance is, and how it compares to what's printed on the capacitor. The capacitors I harvested are outside the measuring range of my DMM, so the easy way would be to just buy a capacitance meter to test them.
I don't always do things the easy way though, especially when there's an opportunity to learn something new. I'm pretty sure I can come up with a workable method to measure the "mystery" capacitors.