Abstract: A portable testing device is disclosed for testing the electrical circuits of power tools and cables having a general three-conductor wiring circuit including a first test station for checking the wiring polarity of an outside electrical receptacle from which the testing device operates and a second test station having a testing circuit and receptacle for receiving a plug of the power equipment being tested for detecting the existence of a defective ground circuit in the power equipment. A third test station is provided for checking the ground continuity of a power tool wiring circuit. A fourth test station is provided for checking the wiring conditions of a three-conductor extension power cable having a three-prong plug carried on one end and a three-socket receptacle carried on the other end.