test double examples
https://lostechies.com/derekgreer/2011/03/29/effective-tests-how-faking-it-can-help-you/ http://xunitpatterns.com/Mocks,%20Fakes,%20Stubs%20and%20Dummies.html https://www.javacodegeeks.com/2015/09/test-double-patterns.html https://adamcod.es/2014/05/15/test-doubles-mock-vs-stub.html