digital design is disclosed the method comprises generating a reference model for a first digital design and creating an operational model for a second digital design wherein the first digital design and the second digital design are intended to have a same logical function a plurality of testcase types are then created by constraining one or more internal signals and one or more test scripts representing the plurality of testcase types are produced the method also includes verifying the second digital design with a testing simulation program by comparing results of the test scripts from the operational model and the reference model application_number US 94495607 A description with reference now to figures and in particular with reference to fig1 there is depicted a block diagram of a data processing system equipped with a hardware simulation and testing system in accordance with a preferred embodiment of the present invention data processing system 100 contains a processing storage unit e g ram 102 and a processor 104 data processing system 100 also includes non volatile storage 106 such as a hard disk drive or other direct access storage device an input output i o controller 108 provides connectivity to a network 110 through a wired or wireless link such as a network cable 112 i o controller 108 also connects.