The image is being tested to be be able to on low resource machine types (f1-micro, g1-small) and high CPU/Mem machine types (n1-standard-96).
The test consists in writing to a file, rebooting and then testing that the file is intact.
The instance prints a custom message "BOOTED" after starting up. After that, a file is stored on disk with the "REBOOT" content, which will be printed after reboot to guarantee that the file is intact.
No setup needed