def METHOD_NAME(vm_name, test):
    """
    Get a disk target dev of the VM.
    :param vm_name: Domain name
    :return: Disk target dev
    """
    disks = vm_xml.VMXML.get_disk_blk(vm_name)
    dev = ""
    try:
        dev = disks[0]
        logging.debug("Use %s of domain %s to do testing.", dev, vm_name)
    except IndexError:
        test.fail("No disk in domain %s." % vm_name)
    return dev