testing functionality that depends on compile-time options

[Alexander von Rhein]

Hi,

I noted that some parameters of busybox functions are not covered in the
test suite (e.g. the -c option of head).
http://git.busybox.net/busybox/tree/testsuite/head
The head -c option is only available if CONFIG_FANCY_HEAD is enabled.
http://git.busybox.net/busybox/tree/coreutils/head.c#n187
I am doing a PhD and I plan to generate and test many busybox
configurations (with different compile-time options enabled/disabled).

So I was wondering whether it occurs often that optional parameters are
not tested.
If that is so, is it because of technical inconvenience (variability
management) or because the implementation not worth a test (trivial)?

Kind regards,
Alexander