[test][tools] Add missing and improve testing

[test][tools] Add missing and improve testing

Mostly this adds testing for certain aliases in more explicit ways.
There are also a few tidy-ups, and additions of missing testing, where
the feature was either not tested at all, or not tested explicitly and
sufficiently.

Reviewed by: MaskRay, rupprecht, grimar

Differential Revision: https://reviews.llvm.org/D71116