Abstract: The testing apparatus comprises two pressure regulators, two pressure gauges or an optional dual pressure gauge, and valve mechanism. In one embodiment the valve mechanism comprises two valves, namely a power actuated three-way air valve and a power actuated four-way air valve controlled by a mode selector. In an alternative embodiment, the valve mechanism comprises a single three-way air valve controlled by a mode selector. The valves are illustrated in the drawings as solenoid operated valves controlled by electrical selector switches. The testing apparatus has an input line or conduit connectable to two pressure ports of a dual pressure indicator and control unit for pasteurizing equipment. In either embodiment illustrated, actuation of the mode selector places the testing apparatus selectively in tracking or differential test modes.