Compilation order during tests

alex88

I’m trying to mock ExTwitter during tests, I’m using GitHub - dashbitco/mox: Mocks and explicit contracts in Elixir · GitHub for that.

In my code I use a config variable to do the Dependency Injection, like this:

config :my_app,
  # DI
  twitter_client: MyApp.TwitterClient

I’ve defined my mock in test/support/mocks.ex as per Mox docs like this

Mox.defmock(MyApp.Mocks.TwitterClient, for: MyApp.TwitterClient)

and in my test.exs config I have

config :my_app,
  # DI
  twitter_client: MyApp.Mocks.TwitterClient

Everything worked while incrementally compiling during development, however on a fresh checkout without any _build folder i get this error:

== Compilation error in file test/support/mocks.ex ==
** (ArgumentError) module MyApp.TwitterClient is not available, please pass an existing module to :for
    lib/mox.ex:92: Mox.validate_behaviour!/1
    lib/mox.ex:84: Mox.defmock/2
    (elixir) lib/kernel/parallel_compiler.ex:121: anonymous fn/4 in Kernel.ParallelCompiler.spawn_compilers/1

if I remove that mock line, compile and add the line back everything works. It seems like it’s trying to compile the mock file first and then the lib folder.

My elixirc_paths is ["lib", "test/support", "test/factories"] so lib comes first, any idea?

I’ve pushed a sample app with the problem in https://github.com/alex88/myapp just run mix test

18 comments

#compiling #troubleshooting

0 3752 18

2017-11-15 17:40:01 UTC

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hassan

Turns out the real solution was to upgrade the version
Didn’t realize I had pinned it at 0.1.0 (C&P from web page, DOH)

Running mix hex.outdated every so often surfaces those things

Post #18

ciroque

Turns out the real solution was to upgrade the version
Didn’t realize I had pinned it at 0.1.0 (C&P from web page, DOH)

Post #17

ciroque

I was experiencing this as well. My solution involved using use MyApp.MyBehaviour. This required that I implement def __using__(_) as so:

defmodule MyApp.MyBehaviour do
  @moduledoc """
  Behaviour definition
  """

  @type entry_attrs_t::map
  
  @callback create_entry(entry_attrs_t) :: any 

  def __using__(_) do

  end
end

and then in test/support/mocks.ex:

use MyApp.MyBehaviour
defmodule Mocks do
  @moduledoc false
end


Mox.defmock(MyApp.MyMock, for: MyApp.MyBehaviour)

kinda hacky, but not horrible…

Post #16

hubertlepicki

Thank you both @alex88 for reporting the issue and @ericmj for finding the solution <3

Post #15

alex88

Just as reference for readers, the pull request @hubertlepicki openend that includes the fix is Use Code.ensure_compiled? vs Code.ensure_loaded? to ensure the module is available by hubertlepicki · Pull Request #17 · dashbitco/mox · GitHub

Post #14

hubertlepicki

I figured it out why it works for me. I have 3 apps in umbrella, and I only mock the interactions where one calls another. So I suppose in my case the clean build works since the app I am about to mock is already always fully compiled (is in_umbrella dependency).

Post #13

alex88

Mine had the problem only on clean builds, it took a while to find that was happening since I had the module to be mocked already compiled when I first added the dependency and everything was ok

Post #12

hubertlepicki

I am trying to figure out why this is not happening on the app I am using mox in. But I guess it simply boils down to me being lucky and compilation order being luckily correct for me.

I submitted a pull request and this should be resolved in next version :).

Post #11