This is an example trying to apply some lessons learned from Uncle Bob's article The little mocker
In this gist first I'll explain what I learned. Then I'll show you what the code does and finally how I tested the code.
When we're making unit test we want to focus on the code we want to test not external dependencies that are not under
our control. To make life easier and being able to test on isolation our code without side effects from the rest
of the world we use test doubles
. Test doubles try to simulate behavior that is in our code but belongs to external agents/objects.