d/t/{control, basic-usage}: Add DEP8 test

Add basic DEP-8 tests. Cherry-pick from:

https://git.launchpad.net/ubuntu/+source/at/commit/?id=184446b10c9ead9a7821c815351c6bf72f4e9f94

The original author of the tests is @utkarsh. I did a clean cherry-pick and left the commit message unmodified, so it doesn't mention that this closes: #985421.