1. A method of operating a computer system to validate test cases for test models comprising operating the computer system to perform steps of: receiving information for a first test model; generating first test cases from the first test model using a test generator; receiving information for a second test model; eliminating one or more test cases from among the first test cases; and for each test case that remains among the first test cases: generating a test model corresponding to said each test case using information for the second test model; and designating said each test case as being valid or invalid depending on whether or not the test generator can generate a test case from the test model corresponding to said each test case.