How to test callback action?

[fuchsberger]

I am struggling to find a way to properly test the default controller action from the documentation for 100 % project test coverage.
The problem is that I can't expect a valid code from the Google callback redirect leaving me only able to test an invalid code.

Any advice would be appreciated!

defmodule AppWeb.GoogleAuthController do
  use AppWeb, :controller

  @doc """
  `index/2` handles the callback from Google Auth API redirect.
  """
  def index(conn, %{"code" => code}) do
    {:ok, token} = ElixirAuthGoogle.get_token(code, conn)
    {:ok, profile} = ElixirAuthGoogle.get_user_profile(token.access_token)
    conn
    |> put_view(AppWeb.PageView)
    |> render(:welcome, profile: profile)
  end
end

[nelsonic]

Great question @fuchsberger 💭
thanks for opening this issue to capture it, 👌

[fuchsberger]

Actually I figured it out. The trick was to use the Mox Library.

Here is what i did:

1. Create two Modules, a stub and a behavior module.

defmodule DsaWeb.ElixirAuthGoogle do
  @callback get_token(String.t, Plug.Conn.t) :: {:ok, map()}
  @callback get_user_profile(String.t) :: {:ok, map()}

  def get_token(code, conn), do: impl().get_token(code, conn)
  def get_user_profile(access_token), do: impl().get_user_profile(access_token)
  defp impl, do: Application.get_env(:dsa, :elixir_auth_google, ElixirAuthGoogle)
end

defmodule DsaWeb.StubElixirAuthGoogle do
  import Dsa.AccountsFixtures, only: [valid_user_attrs: 1]

  @behaviour DsaWeb.ElixirAuthGoogle

  def get_token(code, _conn) do
    if code == "valid_code" do
      {:ok, %{access_token: "valid access token"}}
    else
      {:ok, %{error: "invalid_grant", error_description: "Malformed auth code."}}
    end
  end

  def get_user_profile(access_token) do
    if access_token == "valid access token" do
      {:ok, valid_user_attrs(given_name: "John", family_name: "Doe")}
    else
      {:ok, %{error: "invalid_request", error_description: "Invalid Credentials"}}
    end
  end
end

2. Inside test_helpers.exs define the mock:

Mox.defmock(DsaWeb.MockElixirAuthGoogle, for: DsaWeb.ElixirAuthGoogle)
Application.put_env(:dsa, :elixir_auth_google, DsaWeb.MockElixirAuthGoogle)

ExUnit.start()
# ...

3. In your conn_case.ex enable it for all tests:

  setup _ do
    Mox.stub_with(DsaWeb.MockElixirAuthGoogle, DsaWeb.StubElixirAuthGoogle)
    :ok
  end

4. Add some tests:

defmodule DsaWeb.ElixirAuthGoogleTest do
  use DsaWeb.ConnCase, async: true

  import Mox
  import DsaWeb.ElixirAuthGoogle, only: [get_token: 2, get_user_profile: 1]

  describe "get_token/2" do

    test "does return access_code if valid code", %{conn: conn} do
      assert {:ok, %{access_token: "access token"} == get_token("valid_code", conn)}
    end

    test "does return error if invalid code", %{conn: conn} do
      assert {:ok, %{error: "invalid_grant", error_description: "Malformed auth code."}} == get_token("invalid code", conn)
    end
  end

  describe "get_user_profile/1" do

    test "does return access_code if valid access token" do
      assert {:ok, %{given_name: "John", family_name: "Doe"}} = get_user_profile("valid access token")
    end

    test "does return error if invalid access token" do
      assert {:ok, %{error: "invalid_request", error_description: "Invalid Credentials"}} = get_user_profile("invalid access token")
    end
  end
end

[nelsonic]

@fuchsberger thanks for the reply.
We definitely need to improve the documentation of this package to include clear testing path. 💭

[fuchsberger]

yes behavior and stub should ideally be handled via the package not by the user leaving the user with just two lines to add for testing.

[nelsonic]

@fuchsberger apologies for not being more helpful on my previous replies.
The built-in Mock functionality, or "Test Double" has been included with this package since 2020:
https://github.com/dwyl/elixir-auth-google/releases/tag/v1.2.0

The documentation for it is not great. Sorry. 🤦‍♂️
So I've added docs to the PR: https://github.com/dwyl/elixir-auth-google-demo/pull/16/files#r1102952022