A computer related system and method uses regression testing techniques for testing computer hardware and/or software application(s). Input data and commands from a user are stored on a host, and sent to an interface device, which then sends them to a hardware/software system under test. Visual display data on a visual display device is thereby affected. Signatures (representative of the visual display data) are generated by the interface device as a result of input data and commands sent to the interface device and system under test. These signatures are received and stored by the host. On command of a user, the stored signatures, input data and commands are subsequently sent to the hardware/software system under test, and new signatures are generated. These new signatures are compared with the stored signatures, and the results of this comparison are used as an indication that the hardware/software system under test is performing as expected.