Diodes should be tested two different ways
A resistance check in both directions. Forward biased should show a very high resistance, reverse biased diodes should show "OL".
A barrier voltage check (diode test feature) with a digital multimeter in both directions.
Forward biased should show the barrier voltage, reverse biased diodes should show "OL".
Barrier voltages for silicon typically range from 0.5 - 0.7 volts.
Barrier voltages for germanium typically range from 0.2 - 0.3 volts.
