There are some great notes there.
Nice solutions for OS requirements also.

It seems that if something is missing, you should exit in the Makefile.PL, that's what Devel::CheckLib suggests.

Some of it seems bulky, like checking os.. the use-devel-assertos script is iffy, but dammit it works.

Thank you so much, this is incredibly helpful.

It seems you can basically test these things in the Makefile.PL. If something is missing, you should warn and exit. There is a convention for bailing out on bad os, 'OS UNSUPPORTED' or 'No support for OS'- I'm trying to find out what the warning should be for a missing binary dependency, or lib, etc- per CPAN tester standards.

But my main question is answered, the tests should check the distributed code, not the system setup. The Makefile.PL should make decisions such as missing files, etc.. and should not die but exit with warnings if so.