Who can help explain, when randomize is used as a checker instead of a generator, what scenarios is it generally used in?
In reply to jianfeng.he:
randomize(null) was designed to help with directed tests(non-random), and semi-directed tests. You could manually set random variables and then check if they still met the constraints. Then alter the course of the test depending on the result.
Unfortunately so few people test the result of any randomize() function calls that tools generate noisy warning messages. So this feature is rarely used.