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Chapter.8 Testing MVC

like app logic, must be Fast, Isolated, DRY, Repeatable

ensure your test config are as you need, test.exs

Understanding ExUnit

ExUnit.start ensures it's ready, placed in TestHelper

  • structure
defmodule MyModuleTest do
  use ExUnit.Case, async: true

  setup, do: :ok

  test "#myaction" do
  end
...
  • to run mix test; mix test my/module_test.exs:6 for specificity

Creating Test Data

Testing Contexts

  • Phoenix generates a module test/support/data_case.ex serving a foundation for tests that interact with DB

  • data_case handles setup/teardown of DB integrating with Ecto.Sandbox allowing concurrent transactional tests (transactional tests run tests then rollback changes made during test)

  • add import Videologue.TestHelpers to using do .. end

Testing User Accounts

add , async: true to use Videologue.DataCase

defmodule Videologue.AccountsTest do
  use Videologue.DataCase, async: true

  alias Videologue.Accounts
  alias Videologue.Accounts.User

  describe "register_user/1" do

    @valid_attrs %{username: "testuser", name: "test user", password: "cryptography"}
    @invalid_attrs %{}

    test "with valid data inserts" do
      assert {:ok, %User{id: id} = user} = Accounts.register_user(@valid_attrs)
      assert user.name == "test user"
      assert user.username == "testuser"
      assert [%User{id: ^id}] = Accounts.list_users()
    end
  ...
...

just run this specific test set as mix test test/videologue/accounts_test.exs

  • add tests for authenticate_by_username_and_password/2 with setup block using user_fixture pre-set for password

  • while adding tests for Category in my version, I noticed I haven't added changeset flow for create_categories!/1 which allows nullable names; so fixed that

Using Ecto Sandbox for Test Isolation and Concurrency

  • one of the features provided by DataCase is Ecto Sandbox; its role is to do DB transaction rollbacks

  • it just wraps each test in a transaction, then rollbacks.. enabling concurrent testing with same DB

  • needing aync: true tag

Integration Tests

test the route via endpoint, as a real web request does making sure Controller returns success/redirect/error-codes as desired

Warming Up with PageController

if using PostgreSQL; even here ConnCase can be passed async: true; not with all DBs

  • uses Phoenix.ConnTest to set up API, import convenient aliases

  • ensure to be tested Endpoint is configured

  • setup here return conn if :ok

  • assertion helpers like html_response/2, json_response/2 are available

add import Videologue.TestHelpers to using macro in ConnCase; making fixture functions available in controller tests

Testing Logged-out Users

  • add following for non-auth causing redirects, and run Mix tests by line-number on this script to just check this
  describe "logged-out user" do
    test "gets redirected for all video actions", %{conn: conn} do
      [
        get(conn, Routes.video_path(conn, :new)),
        get(conn, Routes.video_path(conn, :index)),
        get(conn, Routes.video_path(conn, :show, "101")),
        get(conn, Routes.video_path(conn, :edit, "101")),
        get(conn, Routes.video_path(conn, :update, "101", %{})),
        get(conn, Routes.video_path(conn, :create, %{})),
        get(conn, Routes.video_path(conn, :delete, "101")),
      ] |> Enum.each(fn conn ->
        assert html_response(conn, 302)
        assert conn.halted
      end)
    end
  end

Preparing for Logged-in Users

  • don't embed user_id is session for Auth plug to be tricked by, as that could cause leaky implementation

direct request to session controller everytime would be expensive

  • test login mechanism in isolation; build a bypass for rest usecases

add following pat-match for call in auth.ex to ensure if a current_user exists it's honored

def call(conn, _opts) when not is_nil(conn.assigns.current_user), do: conn

now tests for logged-in users are much cleaner

Testing Logged-in Users

  • adding setup %{conn: conn, login_as: username}, do: login(conn, username) like prep functions to make session have user-id for relevant video

Using Tags

  • now to provide login_as: username construct to setup; for each test used with it add @tag login_as: "alice"

  • tag module attribute accepts keyword-list/atom; providing atom is a way to provide flag style attribs

  • can also be used to filter tests as mix run test/videologue_web --only login_as

  • had to {:ok, conn} = recycle(conn) |> conn_assign(user) before every later HTTP request in tests; else it lost user-id in Conn Assigns

  • need to cover negative flows which have been managed for explicitly; so to ensure they don't break.. like access of other user's content

Ecto.NoResultsError gets treated by Plug as 404 hence test-able via assert_error_sent

Unit-Testing Plugs

should test authentication code now, as getting bypassed in Integration Test

  • AuthTest uses setup to bypass_through/3 as authenticate_user puts flash & :browser pipeline in router plugs fetch_flash to set it up

  • our Unit Test depends on other functionality like fetch_flash; here test-helper bypass_through/3 allows to do a request that goes via entire pipeline but bypasses router dispatch

  • performing get on bypass_through accesses endpoint and stops at browser pipeline; here path provided isn't used by Router just stored in connection

  • now we keep this setup for all functions, as without it tests for login/logout will error for session not fetched... which gets prepared by our bypass_through |> get

  • adding tests for call is simple to check if a placed user id in session gets picked into Assigns

  • test time can be reduce by tweaking hashing of passwords for tests only config :pbkdf2_elixir, :rounds, 1 to config/test.exs

Testing Views and Templates

  • since Phoenix templates are just functions in Parent's View modules, can test like any other

Wrapping Up

Part.II Chapter-09 Watching Videos