My non fail proof but handy way is to remove the cap. from 
the circuit and connect your VOM to the terminals and watch 
the voltage dissipate. The set the VOM to Ohms and 
reconnect the meter to the cap. and you should see the 
resistance steadily go up close to infinity. You are 
actually charging the cap. with the battery in the VOM. 
Then recheck the voltage and you should have a low charge 
and then it will dissipate again. Good cap. via non fail 
proof test.