This is a companion discussion topic for the original entry at https://thoughtbot.com/upcase/videos/isolated-unit-testing
One thing I was hoping would be touched on is the coupling to implementation that mocking can create, any thoughts?
At 8:45, line 18 I believe you should be injecting the
mailing_list collaborator in addition to
Otherwise, the unit/system under test wouldn’t know what a
mailing_list was in case anyone got confused by that.