For the low-voltage testing of the board, you need a dummy microcontroller.
There are two ways of assembling the dummy microcontroller:
Using a prototyping board
Make a circuit based on the schematics below:
The side with the arrow goes towards the top of the SHVPS board.
Using a PCB
The files to make the PCB are in the download section. It is included as a project in the Altium file of the HVPS PCB (file LV_tester.PrjPCB), or available in Gerber format. The components you need are listed in the Bill of Material file (BOM-SHVPS.xlsx) available in the download section in the tab “Low-voltage-tester”. It simply consists in a switch, a 220 Ohm resistor, a LED, and 2x 17-pin headers. The two white lines (on the side opposite the switch) represents the USB connector of the real arduino micro and must match the white lines printed on the SHVPS board (i.e. the top of the board).