GSoC: Questions about test

[As Ss]

I noticed some files have little code coverage and I tried to add
tests for them.  But some of them are not system call function like
upeek in src/upeek.c. Is there any way to make the test cover these
functions such as upeek and mmap_cache_enable?
And I find that sysctl is not yet covered. From the man page, sysctl
was removed in linux 5.5. Is it worthwhile to add a test for it?