Conflicts between Mox, behaviours and optionnal arguments

Questions & Help Questions
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13

Maybe it’s just my perspective, but I usually introduce a behaviour only when I need more than one implementation of the same “behavior”. Adding a behaviour solely to enable mocking in tests has always felt a bit off to me.

e.g.

defmodule Boo do
 use Genserver
 
 def get_market_data() do
    ....
 end
end

vs

defmodule BooBehvaiour do
  @callback get_market_data() :: data
end

defmodule Boo do
 use GenServer
 @behaviour BooBehvaiour
 
 @impl
 def get_market_data() do
    ....
 end
end

Reading our discussion I think there’s also a chance we’re talking about two different things :sweat_smile:

Could you walk me through what I should do if I want to test a piece of logic that depends on Boo.get_market_data/0, but I don’t want to start a process or mock all the underlying HTTP/DB calls? I’d just like to mock the return value of get_market_data() function to keep the test simple and async - how would you approach that? adding behavior to Boo?