How to build a backend that can return raw data (for testing) as well as html for templating

[peerreynders]

Have a look at:

Application communication best practices

On a single node that is usually accomplished with “parallel dependencies” (poncho projects within Nerves). For example from an elixir course: game.ex is “the hangman” backend to “the gallows” phoenix application. And game.ex isn’t even a process - it simply defines a struct which captures the state that is manipulated only through the module’s functions. The hangman backend does have it’s own server but that is only run for use with the text client.

i.e. create a UI independent OTP application that deals with the business logic and data which a Phoenix app can then use as a dependency - acting only as the web front end.