An imaging system may include a pixel array having a plurality of image pixels and a plurality of test pixels. The test pixels may each include a photodiode configured to receive a test voltage. For example, the photodiodes of test pixels may be coupled to a bias voltage supply line or the photodiodes may receive test voltages via a column readout line or a row control line. The test voltage may be output on a column line associated with the column of pixels in which the test pixel is located. Verification circuitry may compare the output test signal with a predetermined reference signal to determine whether the imaging system is functioning properly. If an output test signal does not match the expected output signal, the imaging system may be disabled and/or a warning signal may be presented to a user of the system.