comm: don't use files for test

[sylvestre]

having the content and expected results helps a lot to debug

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/misc/dircolors is no longer failing!
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

[cakebaker]

Yes, I agree, the tests are much easier to read without the fixtures. Thanks for removing them :)

[sylvestre]

Thanks. i wonder if we should do that for other programs