If you mean testing the "disable Landlock if the headers and syscalls are out of sync" functionality then I agree, workarounds for such corner cases are often not fully tested.

But it would have been enough here to have a test just to see that Landlock works in general. That test would have broken with this commit, because that's what the commit actually does - break all Landlock support.

Based on that it sounds like there wasn't a test for Landlock integration, if I've understood things correctly.