How do i test capacitors?
Charge thru a resistor to the working voltage.  Choose a resistor so RC (where R is the resistance, C is the capacitance, and RC is the time constant) is workably large.  The final voltage should equal the applied voltage - IR, where I is the leakage current.  The rate of charge will give you C ( if I is large you will need to correct for that )  This ignores the burden of the meter which is probably above 1 meg and for a supply cap probably does not matter.