You still can test them when they are private, just make sure that your tests have the correct alias-prefix.
Also similar to the proposed iex helper, some ex_unit helper would be thinkable as well, but I’m not sure if that is really necessary.
Last but not least, is this a library or a standalone application? If its the latter, hiding the modules might not be necessary at all. If it is a library though, I’d hide the modules by either @moduledoc false or the proposed defmodulep.
