A verification system and method for verifying operation of an HDL (Hardware Description Language) design of a computer system component are disclosed. The computer system is configured to interface between a first bus and second bus. During verification, a simulated model of the HDL design is coupled to a simulated first bus and a simulated second bus. A designated stimulus is applied to the simulated model through the simulated first bus. A stimulus file stored in the computer system memory is configured to specify the designated stimulus to be applied. In response to the designated stimulus, the simulated model initiates bus cycles on the simulated second bus. A transaction checker is provided in the computer system memory to receive information relating to these bus cycles from said simulated second bus. By employing two different busses--one to apply a stimulus and the other to resolve the bus cycle through transaction checking--an effective decoupling of test stimulus from the checking environment is achieved. Due to decoupling, the test environment can be made more robust, and can be used to generate random responses, remap memory, inject errors into data streams etc.