Here are the issues concerning the CSS part, we encountered with @julien-deramond.
The commits can be splited if needed or wanted or even be in another PR. I'm open to every comment that could help fix these issues.
Tackled by the PR:
Typo with (https://github.com/twbs/bootstrap/pull/36398/commits/5b133f5206fbb2d2196d447217c94c5e7c71c2a6)
Carousel test typo error with maybeEnableCycle.
Test improvement with (https://github.com/twbs/bootstrap/pull/36398/commits/41c228b67715c26013f7ac048aa73d4c832a8a04)
Carousel test since the test looked weird to me (Calling the function and expected to be called)
Spy declaration with (https://github.com/twbs/bootstrap/pull/36398/commits/505175a553718f497ca6a07e0b4e4904ea8e6c49)
Make the spy declaration almost the same everywhere to be more consistent. Not sure if this is mandatory.