Abstract: Programs which control conventional computerized test systems must be changed when a particular test instrument controlled by the system is changed to a different test instrument. In accord with this invention, the need for such program changes is minimized by utilizing a generic instrument interface for each class of test instruments. A separate specific instrument interface, which corresponds to the specific instrument to be utilized within the general class, is identified in accordance with global variables and a look-up table based upon the general instrument interface called for in the basic test program. A simulator interface is also provided to facilitate the debugging of a basic test program by generating simulated data responses as if an actual test instrument was connected.