A circuit testing device for providing a number of features to assist in testing electrical circuits in a vehicle. The circuit testing device generally includes a housing having a plurality of testing components positioned thereon and therein. The housing generally includes a light source such as an LED for assisting in illuminating dark spaces. The housing also includes a probe for closing connections and an incandescent bulb for testing purposes. A polarity switch is provided to quickly and easily reverse polarity of the probe. A circuit breaker and circuit activation switch are also provided. By utilizing the present invention, circuit integrity as well as electrical testing of various components (both high voltage and low voltage) of a vehicle may be efficiently performed.