For this test, you will need

Atari Computer
FujiNet
a micro SD card containing the contents of the following file: Micro SD Card ZIP, uncompressed onto it.

Steps

Uncompress the contents of the above file onto a blank SD card, using a suitable computer.
Insert the micro SD card into the FujiNet.
re-connect the FujiNet to the Atari computer, attaching USB power.
Power on Atari.
Wait for CONFIG to boot, and HOSTS/DRIVES to appear.
Edit the first host slot by pressing E.
Change the field to SD and press RETURN.
Press ENTER to select the host slot.
Verify that the contents of the flash card are visible.
Select the Atari DOS folder. The Atari DOS disk images should appear.
Select the Atari DOS 2.0s.atr file. The mount to device slot screen should appear.
Select the first device slot. The message should change to ask for mount as R or W, select either. The hosts/drives should re-appear.
Press OPTION to boot.
if READY appears, type DOS and press RETURN
The DOS menu should appear.
Test done, power off system.

The microSD Contents ZIP was updated due to corrupted DOS 2.0S image. (2020-07-27)