1. A computer software product, including a non-transitory computer-readable medium in which computer program instructions are stored, which instructions, when read by a computer, cause the computer to perform a method for functional verification of a design, having an operational space comprising the steps of: accepting as an input a test template that specifies test parameters directed to controlling production of transactions that exercise a function of said design, said template comprising constraints and variables covering a working space within said operational space, said working space comprising a legal domain for generation of test cases by a test generator; associating an exemption mode of operation with at least one of said constraints or at least one of said variables, wherein a domain of said at least one of said variables is modified or said at least one of said constraints is disabled in said exemption mode of operation; producing a test case that lies inside said operational space and outside said working space of said design by enabling said exemption mode of operation, said test case comprising a series of randomly generated transactions originating from said template, wherein said transactions exercise said function of said design, said test case being legal according to a specification of said design; submitting said test case for execution by said design; responsively to said execution detecting an unpredicted flaw in said design; and exposing an indication of said unpredicted flaw.