The only supported method of automated testing is by using the "Bootable Diagnostics - Automated Testing" option from the Service Center boot menu. Since normally the automated test environment is not the default, you will need to change the configuration files on the USB device (this method will not work when booting from the CD). To change the boot configuration files, please follow these steps:
Plug the Multipurpose USB Device into a known good computer
Open the following directory: E:\isolinux.
(Change the E: as needed to access the USB Device)
After making a backup copy of each, open the following files with a feature rich text editor (such as Notepad ++):
live_486.cfg
live_amd64.cfg
change ontimeout to pcd_automated_64 or 32 depending on which file is
being modified
Save your changes onto the USB device
If the system is UEFI you might also need to change:
grub.cfg and grub32.cfg files located on your USB MUD at: boot\grub
To change the default boot selection just modify the "0>0" The first 0 selects the boot option for the submenu, 0 being submenu "Service Center Bootable Diagnostics" 1 being submenu "Service Center for Android"
the second 0 determines the menuentry for that submenu starting at 0.
I would then recommend testing your new configuration on a known good system (with a monitor), just to make sure. If at any time you need to return the configuration to its default, simply re-image the USB device using the Diagnostics CD.
Note that even if the system is booting, without video, you may not be able to set the MUD as the primary boot device, making the above into a purely educational experience.