Looks like you never heard of BIT (built in test) program
Oh yes, I have, I have also heard of playing solitaire.
A lot of the BIT stuff is a leftover from the vacuum tube days (tubes, ok valves to the British, wear out). Another reason for BIT was core memory, remember those?.

If a product is essential enough to justify a test, testing the hardware makes absolutely no sense, the only test that has any validity is a test for functionality of the system.

Erik