A device for testing a power supply. The device includes a modulation generator, and a connection between the modulation generator and the power supply under test through which a load is injected to the power supply under test. A resistive load generator applies a resistive load to the power supply. A reactive load generator applies a reactive load to the power supply. A load selector selectively applies the resistive load and/or the reactive load to the power supply to be tested. The device further includes a discharge network that automatically or manually discharges capacitors of the device.