Methods and systems are provided for testing a physical hardware device by a virtual hardware device using a virtualization system. The methods and systems perform operations including determining a memory location of a variable through which the virtual hardware device exchanges information with an external hardware resource. The operations also include exchanging the information with the external hardware resource via the memory location of the variable. The memory location of the variable used by the virtual hardware device is the same as a memory location of the variable used by the physical hardware device.