Abstract: A portable field tester for a circuit breaker having an electronic trip unit includes a ribbon cable having a connector plug for making connection to a restraint plug socket of the trip unit. The tester has a parallel connector in which the breaker rating plug may be inserted. A battery source is included and a battery fail LED is illuminated if the source voltage falls below a certain level. A voltage regulator and a plurality of voltage dividers develop reference test voltages for application to the breaker trip unit via the connectors and cable. Switches selectively disable a ground fault test circuit in the breaker during primary injection testing. A pair of resistors are connected via the cable and connectors for rapidly discharging the breaker memory circuits after each test.