As requested by kylo, opening a ticket for these gaps in testing.
Currently, there are no unit tests that I could find for cross-resource auto-dependencies.
For example, we see in lines 380-402 of user that groups managed by Puppet which a user is added to are autorequired. If you consult user spec, there are no tests for this type of auto-dependency.
One of my objectives in
PUP-6099 was to figure out how to do this kind of testing and it appears I succeeded. There is a test for mount resources autorequiring and autobeforing file resources.
I think it would be worthwhile for these test gaps to be filled since it appears I have figured out how to create them and what I have done can hopefully be used as a code template.