Abstract: Automatic test equipment for testing hydraulic/pneumatic devices which devices are included within the test system as well as those which may be attached to the test system. Object oriented programming preferably using C++ language is utilized. Abstract classes representative of characteristics of a group of devices to be tested are provided. Also provided are subclasses characteristic of types of units to be tested. Upon declaration of a specific instance of a type of unit to be tested, the abstract class is inherited into a subclass which in turn is incorporated into the unique characteristics for the declared unit to be tested. A test program is activated for the specific unit to be tested. The test program is also constructed by utilizing abstract and subclasses of information characteristic to the unit to be tested.