Follow-up from "Tests: unskip existing RPC + refactoring"

The following discussion from !2130 (merged) should be addressed:

• @arvidnl started a discussion: (+1 comment)

  Nit-picky: if there is a technical reason why not (e.g. "this is complicated to test because ...") and not just that no-one have had the time to get around to doing it, then it would be worth to mention here. That would also apply to the other skipped tests. But not a biggie...