I probably wasn't being clear about STDOUT on the ruby version. I just didn't do it in this particular project for the ruby version. I just tested that the flags didn't throw anything. I had tests on other production tools and yeah $stdout saving is nice.

Someone mentioned on reddit me about a CLI testing framework that perhaps does a more holistic job of testing STDOUT.

--> https://bitheap.org/cram/

it's written in python but it's not for python projects per se.