This is a guide on how to email securely.
There are many guides on how to install and use PGP to encrypt email. This is not one of them. This is a guide on secure communication using email with PGP encryption. If you are not familiar with PGP, please read another guide first. If you are comfortable using PGP to encrypt and decrypt emails, this guide will raise your security to the next level.
In many production systems you'll want to have one module capable of talking to many potential implementations of a collaborator module (e.g a in memory cache, a redis-based cache etc). While testing it's useful to control which module the module under test is talking to.
Here are the approaches I can see. The two points that seem to divide the approaches are their tool-ability (dialyzer) and their ability to handle stateful implementations (which need a pid).
Modules are first class, so you can pass them in. Used in EEx, where passed module must implement a behaviour.
