UPDATE: Almost 2 years later we have released a tiny library called Mox for Elixir that follows the guidelines written in this article. A couple days ago I expressed my thoughts regarding mocks on Twitter: Mocks/stubs do not remove the need to define an explicit interface between your components (modules, classes, whatever). [1/4] — José Valim (@josevalim) September 9, 2015 The blame is not on moc