quoted

So, I'm wondering, whether there is an example or guidelines that is
worth to follow.

It all depends on what you want to test.  There is no "general" way to
do this as all subsystems / parts of the kernel are different.

I'd like to add more tests in lib/test-hexdump.c. To my mind, I have 2 options:
follow the current style, or perform a bit of reorganization. I'm
inclined to the
second one given that the addition of new tests may lead to unreadable code.
But I doubt which way is better in this case.