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