A testing apparatus compatible with an electrical outlet is presented here. The outlet has a line socket designated for a line voltage conductor, a neutral socket designated for a neutral voltage conductor, and a ground socket designated for a ground voltage conductor. The testing apparatus includes a housing, a plug interface having an electrically conductive ground prong configured to mate with the ground socket, a first indicator lamp having a first terminal electrically coupled to the ground prong, and an electrically conductive lead extending from the housing. The conductive lead has a proximal end electrically coupled to the second terminal of the indicator lamp, and a distal end terminated with an electrically conductive connector. The indicator lamp is activated in response to a voltage differential between the ground prong and the electrically conductive connector.