- https://martinfowler.com/articles/mocksArentStubs.html
- https://blog.pragmatists.com/test-doubles-fakes-mocks-and-stubs-1a7491dfa3da
- https://testing.googleblog.com/2013/07/testing-on-toilet-know-your-test-doubles.html
- http://xunitpatterns.com/Test%20Double.html