thoughtbot/shoulda-matchers — pull request #420 by mcmire (2014-01-17 18:19:10+00:00)
Title: Association matchers support :autosave option

has_one, has_many, belongs_to, and has_and_belongs_to_many relationships can
have an `:autosave` option, which causes the relevant associated records to be
automatically saved when their parent is saved.

This is based on a PR by @calebthompson (#125), which I've brought up to date
with master.