Databases, APIs, Cache, basically entire services. The idea here (a according to the elixir community ) is to create a contract and then create an implementation for that contract as well as a mock ( or a fake implementation ).
Then depending on the environment you either use the real object or a mock that implements the contract. ( do note that by definition, your real object also implements the contract ).
I am still not convinced with mocks, I pretty much prefer to simply pass the functions I am going to need down the line ( Functional DI, shout out to @peerreynders for the video link ).
The issue with this is that your higher level functions will have a ton of dependencies, no matter what … So I guess this is where the argument for mocks could take place …
