collection.ex

defmodule Digraffe.Collection do
  use Digraffe.Web, :model

  alias Digraffe.Settings

  schema "collections" do
    field :title, :string
    belongs_to :owner, Settings
    timestamps
  end

  @required_fields ~w(title owner_id)
  @optional_fields ~w()

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
  end
end

error output

  1) test allows setting of the selected collection (Digraffe.SettingsTest)
     test/models/settings_test.exs:12
     Assertion with == failed
     code: collection.id() == updated.selected_collection().id()
     lhs:  "fb444450-5562-4356-90fc-858401a2987e"
     rhs:  "8c20c15c-d970-4230-bfb3-f80fc35f1119"
     stacktrace:
       test/models/settings_test.exs:23



Finished in 0.6 seconds (0.5s on load, 0.03s on tests)
65 tests, 1 failure, 64 skipped

Randomized with seed 854580

settings.ex

defmodule Digraffe.Settings do
  use Digraffe.Web, :model

  alias Digraffe.{Repo, Settings}

  schema "settings" do
    field :name,        :string
    field :provider,    :string
    field :provider_id, :string
    field :avatar_url,  :string
    has_many :collections,         Digraffe.Collection, foreign_key: :owner_id
    has_one  :selected_collection, Digraffe.Collection, foreign_key: :id
    timestamps
  end

  @required_fields ~w(name provider provider_id avatar_url)
  @optional_fields ~w()

  def changeset(model, params \\ :empty) do
    model
    |> cast(params, @required_fields, @optional_fields)
    |> cast_assoc(:selected_collection)
    |> unique_constraint(:provider_id)
  end

  def get_or_create(user) when is_map(user) do
    case get_settings(user) do
      nil   -> changeset(%Settings{}, user) |> Repo.insert!
      model -> model
    end
    |> Repo.preload(:selected_collection)
  end

  def get_or_create(nil), do: nil

  defp get_settings(%{} = user) do
    case Repo.get_by(Settings, user) do
      nil      -> nil
      settings -> Repo.preload(settings, :selected_collection)
    end
  end

  def small_avatar_url(settings) do
    ~s(#{settings.avatar_url}&s=40)
  end
end

settings_test.exs

defmodule Digraffe.SettingsTest do
  use Digraffe.ModelCase
  import Digraffe.Factory
  alias Digraffe.{Settings, Collection}

  test "#small_avatar_url is added" do
    settings = %Settings{avatar_url: "http://avatar/url?v=1"}
    assert "http://avatar/url?v=1&s=40" == Settings.small_avatar_url(settings)
  end

  @tag wip: true
  test "allows setting of the selected collection" do
    settings = create(:settings) |> Repo.preload(:selected_collection)
    refute settings.selected_collection
    collection = create(:collection)
    changeset = settings
      |> Ecto.Changeset.change()
      |> Ecto.Changeset.put_assoc(:selected_collection, collection)
    assert changeset.valid?
    updated = Repo.update!(changeset) |> Repo.preload(:selected_collection)
    assert collection.title == updated.selected_collection.title
    # This assertion is failing
    assert collection.id == updated.selected_collection.id
  end
end