Described is a method, system, and computer program product that provides control of a hardware/software system, and allows deterministic execution of the software under examination. According to one approach, a virtual machine for testing software is used with a tightly synchronized stimulus for the software being tested. A verification tool external to the virtual machine is used to provide test stimulus to and to collect test information from the virtual machine. Test stimulus from the verification tool that is external to the virtual machine provides the stimulation that incrementally operates and changes the state of the virtual machine. The stimulus is created and coverage is collected from outside the virtual machine by first stopping the virtual machine, depositing stimulus, and then reading coverage directly from the virtual machine memory while the machine is stopped.