Disclosed herein are devices (100), systems, and methods for testing a circuit (114). A circuit test device (100) includes a housing (102) and a circuit (104) disposed in the housing (102). The circuit (104) includes an electromagnetic field (EMF) sensor (106) and a signal detector (110) coupled to the EMF sensor (106). The circuit test device (100) includes an interface (112) connected to the circuit (104) and extending through the housing (102). The interface (112) is adapted for coupling the circuit (104) to a circuit under test (CUT) (114). The EMF sensor (106) is configured to generate a signal in the presence of a time varying flow of current from the CUT (114) in the circuit (104). The EMF sensor (106) is configured to provide the signal to the signal detector (110).