Background
I have an app called :my_app that has a dependency called :my_dep. :my_dep connects to the internet and downloads a bunch of files. Every time I run :my_app, it executes :my_dep because :my_dep is a runtime dependency. So, when I run tests, launch the app in my DEV environment or simply run it, :my_dep always connects to the internet to download files.
If :my_dep cannot connect, it fails, and because it is a runtime dependency, :my_app fails to launch.
My Approach
The current system means I can’t run local tests nor do anything without a connection to the internet. So my attempt at fixing this was to follow the approach suggested by mocks and explicit contracts and to create an interface (add a boundary between :my_app and :my_dep) and to create a mock that implements the interface.
Following is an example of how I am implementing this technique:
Geolocation Module of MyApp:
defmodule MyApp.Geolocation do
@geo Application.get_env(:my_app, :my_dep_api)
require Logger
@spec geolocate(String.t) :: String.t
def geolocate(ip) do
ip
|> @geo.find()
|> get_country(ip)
end
@spec get_country({:ok, [String.t]}, String.t) :: String.t
defp get_country({:ok, [country | _tail]}, _ip), do: String.upcase(country)
end
DEV config file of MyApp:
config :my_app,
my_dep_api: MyDep.StaticMock
The StaticMock file:
defmodule MyDep.StaticMock do
@behaviour MyApp.IMyDep
@behaviour MyApp.IMyDep
@spec find(String.t) :: {:ok, [String.t]}
def find(_ip), do: {:ok, ["ES", "cat", "b"]}
end
Problem
The issue here, is that when I launch my app in DEV, it still runs the original my_dep app and it still tries to connect and download the files.
Question
How can I fix this?
