> Was the plan to add an entire make file or something?

I don't understand what do you mean by this.

> I think just checking that rdmd isn't mangling the paths in unexpected ways would be enough, no?

Yes, but is not so simple, the problem is the input data for the test :)
And I'm really, really sorry but I don't have the time to dedicate to build a good rdmd test suite. I think I did a fair job by testing what I changed, but I think making a proper test suite for rdmd is beyond the scope of this PR.