Does glibc has complete test coverage?

[Peng Yu]

Hi,

https://www.kernel.org/doc/man-pages/missing_pages.html

"... quite a few kernel and glibc bugs have been uncovered while
writing test programs during the preparation of man pages. "

I see the above text. It doesn't make too much sense, as it indicates
that glibc does not have complete test coverage.

Why not taking an approach of always accompanying each line of source
code with appopriate test cases? If this approach is taken, then most
bugs should have been eliminated beforehand?

-- 
Regards,
Peng