This disclosure concerns the co-design of a testbench (100) and driver (102) of a device. It is an advantage in at least some embodiments that it improves driver reliability and reduces development cost. It does this by re-using the device functional layer (70) that is dependent on the device class but independent of the specific device and specific operating system (OS) of the driver. The device functional layer (70) is re-used as it is implemented in the device's testbench (100) and also as the core part of the device (driver (102). A scenario layer (68) is also used that is able to test the generic device interface (72) and device functional layer (70) in the testbench (100) environment, and the testing includes testing for responses to OS requests. This helps provide more exhaustive testing.