Add tests around removing games from a user's collection

Author: Chris Rees

lib/agoneum/account/account.ex

@@ -125,12 +125,27 @@ defmodule Agoneum.Account do
   """
   def add_games(%User{} = user, %Game{} = game), do: add_games(user, [game])
   def add_games(%User{} = user, games) do
-    game_changesets = Enum.map(games ++ user.games, &Ecto.Changeset.change/1)
+    game_changesets = games ++ user.games
+                      |> Enum.map(&Ecto.Changeset.change/1)
                       |> Enum.uniq()
 
     user
     |> change_user()
     |> Ecto.Changeset.put_assoc(:games, game_changesets)
     |> Repo.update()
   end
+
+  @doc """
+  Removes a game (or games) from the user's collection.
+  """
+  def remove_games(%User{} = user, %Game{} = game), do: remove_games(user, [game])
+  def remove_games(%User{} = user, games) do
+    remaining_games = Enum.reject(user.games, fn(game) -> Enum.member?(games, game) end)
+    game_changesets = Enum.map(remaining_games, &Ecto.Changeset.change/1)
+
+    user
+    |> change_user()
+    |> Ecto.Changeset.put_assoc(:games, game_changesets)
+    |> Repo.update()
+  end
 end

lib/agoneum/account/user.ex

@@ -17,7 +17,7 @@ defmodule Agoneum.Account.User do
 
     field :admin, :boolean, default: false, null: false
 
-    many_to_many :games, Agoneum.Games.Game, join_through: "user_games"
+    many_to_many :games, Agoneum.Games.Game, join_through: "user_games", on_replace: :delete
 
     timestamps()
   end

lib/agoneum/games/game.ex

@@ -16,7 +16,7 @@ defmodule Agoneum.Games.Game do
     field :name, :string
     field :year, :integer
 
-    many_to_many :users, Agoneum.Account.User, join_through: "user_games"
+    many_to_many :users, Agoneum.Account.User, join_through: "user_games", on_replace: :delete
 
     timestamps()
   end

test/agoneum/account/account_test.exs

@@ -154,5 +154,43 @@ defmodule Agoneum.AccountTest do
 
       assert List.first(user1.games).id == List.first(user2.games).id
     end
+
+    test "remove_games/2 removes a game from the user's list" do
+      user = user_fixture()
+      game = game_fixture()
+      game2 = game_fixture(%{name: "BANG! High Noon"})
+
+      {:ok, user} = Account.add_games(user, [game, game2])
+      assert length(user.games) == 2
+
+      {:ok, user} = Account.remove_games(user, game)
+      assert length(user.games) == 1
+      assert List.first(user.games).name == "BANG! High Noon"
+    end
+
+    test "remove_games/2 removes multiple games from the user's list" do
+      user = user_fixture()
+      game = game_fixture()
+      game2 = game_fixture(%{name: "BANG! High Noon"})
+      game3 = game_fixture(%{name: "BANG! Fistful of Cards"})
+
+      {:ok, user} = Account.add_games(user, [game, game2, game3])
+      assert length(user.games) == 3
+
+      {:ok, user} = Account.remove_games(user, [game, game3])
+      assert length(user.games) == 1
+      assert List.first(user.games).name == "BANG! High Noon"
+    end
+
+    test "remove_games/2 returns the original game list if the game being removed is not present" do
+      user = user_fixture()
+      game = game_fixture()
+      game2 = game_fixture(%{name: "BANG! High Noon"})
+
+      {:ok, user} = Account.add_games(user, game)
+      {:ok, user} = Account.remove_games(user, game2)
+      assert length(user.games) == 1
+      assert List.first(user.games).name == "BANG!"
+    end
   end
 end