Some embodiments of a power supply monitor include a measurement circuit to measure a voltage provided to the power supply monitor, a comparator to compare the voltage to a predetermined voltage threshold, and an interface to provide, during a scan test of a processing device including the power supply monitor, a fault signal in response to the voltage being below the voltage threshold. Some embodiments of a method include providing a first test pattern to one or more power supply monitors associated with one or more circuit blocks in the processing device and capturing a first result generated by the power supply monitor(s) based on the first test pattern. The first result indicates whether a voltage provided to the circuit block(s) is below a voltage threshold.