1. A computer program product in a computer-readable medium for verifying a digital design in a data processing system, said computer program product comprising: a computer-readable medium; instructions on the computer-readable medium for generating a reference model for a first digital design; instructions on the computer-readable medium for creating an operational model for a second digital design, wherein said first digital design and said second digital design are intended to have a same logical function; instructions on the computer-readable medium for creating a plurality of testcase types by constraining one or more internal signals within said operational model, wherein said plurality of testcase types include a plurality of descriptions of simulated inputs to said reference model and said operational model and constraining one or more output signals from a simulated component within said second digital design; instructions on the computer-readable medium for producing one or more test scripts representing said plurality of testcase types; instructions on the computer-readable medium for verifying said second digital design with a testing simulation program by comparing results of said test scripts from said operational model and said reference model; and instructions on the computer-readable medium for outputting a result of said comparing to a log in said data processing system.