Test them with a 9V battery and say 470 ohms current limit resistor.... I have a LED tester here, very handy as I can test at different currents easily. Its one of those must have tool box testers. 2nd must have is a 2.50000000V voltage reference, handy for checking multimeter calibration plus other things.
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You can test with a VOM in the ohms measuring mode. The red lead is 2 volts and that is enough to energize even blue and white LEDs. You will easily see them come on faintly, even in a moderately lit room. The current is in microamps, so the resistance will show off scale high. The meter is just a handy, safe, current limited power supply.
And of course, test in both directions. The direction that lights is the forward direction.
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His two other posts show he's (she's?) very interested in diodes and LED's specifically. I test LED's with a multimeter like that too, it's usually faster than grubbing around for a battery and an appropriate resistor. If the ohms tester won't do it, try its lowest range. The diode test mode definitely will, if the meter has one. NSFLD! (Not Safe For Laser Diodes).