refactor specs using .first || create to be more deterministic

Created by: adipasquale

https://trello.com/c/gJMG0HBY/945-rendre-les-associations-dans-les-tests-plus-deterministes-plus-de-first

this is more verbose but it makes much more sense and shows what is required explicitly in the specs, and avoids randomness of specs depending on the order they run in