Randy - to test those you could just reverse bias them. Use a series R to ground and a DC voltmeter to read the leakage current indirectly as a voltage across the sense resistor. +20V (or more) to the cathode, DUT ("diode" under test), anode to 100K. Connect the supply and DVM common to the other end of the 100K.+15-20V to the cathode and a series resistor of 100K on the anode to ground. 1 nA would be equal to 100 uV.
You'll need a good DVM. 100K will provide 100 uV for every 1 nA of Il. The series R could also be 1 meg to give you 1 mV/nA but you'll have some significant measurement error due to the DVM's input impedance.
The bias current of the 1510 1512 is quite large: 14 uA max. A diode with 100 nA of Il isn't going to be a deal-breaker when compared to 14 uA. But, very high Il will cause offset when it becomes a significant percentage of I bias. My hunch is that very high values of Il will also increase noise.