Ensuring Elixir Application Performance with Testing and ExUnit/

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Testing the Happy Path for Create

Testing the Happy Path for Create

Learn how to write a happy path test for the create endpoint.

We'll cover the following...

Let’s take a look at the create endpoint. This is the endpoint hit by the form rendered by our previous endpoint for new.

Controller

Let’s take a look at the code and discuss what we’ll need to test:

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#file path -> lib/not_skull_web/controllers/user_controller.ex
def create(conn, %{"user" => user_params}) do
  case Accounts.create_user(user_params) do
    {:ok, user} ->
      Email.send_welcome(user)
      conn
      |> put_session(:user_id, user.id)
      |> put_flash(:info, "Your account was created successfully!")
      |> redirect(to: Routes.user_path(conn, :show, user))
    {:error, %Ecto.Changeset{} = changeset} ->
      render(conn, "new.html", changeset: changeset)
  end
end

There’s branching logic in this function, depending on the success of Accounts.create_user(user_params). As a result, we know that we’ll need at least two tests, a happy path test and an error test.

Happy path test

There are four new code elements that we haven’t tested before:

  1. Sending an email (an outside call as a side effect)
  2. Setting values in the session
  3. Setting the flash
  4. Redirecting a call.

Let’s write our happy path test first since it’s where we’ll cover these. Open up the test file user_controller_test.exs and add a new describe block and test as follows:

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#file path -> test/not_skull_web/controllers/user_controller_test.exs
describe "POST /users" do
    test "success: creates_user, redirects to show page when user is created",
         %{conn: conn} do
      params = Factory.atom_params(:user) 
      expect_email_to(params.email) 
      conn = post(conn, Routes.user_path(conn, :create), user: params)
      assert %{id: id} = redirected_params(conn) 
      assert redirected_to(conn) == Routes.user_path(conn, :show, id) 
      assert %{"user_id" => ^id} = get_session(conn) 
      assert get_flash(conn, :info) =~ "success" 
      user_from_db = Repo.get(User, id) 
      fields_to_check = Map.keys(params) -- [:password]
      assert_values_for(
        expected: params,
        actual: user_from_db,
        fields: fields_to_check
      )
      assert user_from_db.password
    end
end

Let’s see the details of the test:

  • It inherits a Plug.Conn from the test setup.
  • On line 5, we’re getting valid parameters from our factory.
  • Line 7 calls out to a
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