Add comprehensive test coverage for transaction protection

- Add test for card dealing with 3 players (verify all cards dealt)
- Added test for 4 players (verify even 13-card distribution)
- Add test for 5 players (verify uneven distribution with modulo)
- Tests verify atomic transaction behavior
- Tests verify game.started_at is set correctly
- Increases coverage for show.ex transaction code paths

Related to #2343

Author: immortal71

copi.owasp.org/test/copi_web/live/game_live/show_test.exs

@@ -46,9 +46,9 @@ defmodule CopiWeb.GameLive.ShowTest do
 
     test "successfully starts game with 3+ players", %{conn: conn, game: game} do
       # Add 3 players
-      {:ok, _player1} = Cornucopia.create_player(%{name: "Player 1", game_id: game.id})
-      {:ok, _player2} = Cornucopia.create_player(%{name: "Player 2", game_id: game.id})
-      {:ok, _player3} = Cornucopia.create_player(%{name: "Player 3", game_id: game.id})
+      {:ok, player1} = Cornucopia.create_player(%{name: "Player 1", game_id: game.id})
+      {:ok, player2} = Cornucopia.create_player(%{name: "Player 2", game_id: game.id})
+      {:ok, player3} = Cornucopia.create_player(%{name: "Player 3", game_id: game.id})
 
       {:ok, view, html} = live(conn, "/games/#{game.id}")
 
@@ -61,6 +61,20 @@ defmodule CopiWeb.GameLive.ShowTest do
       # Verify game was started
       {:ok, updated_game} = Cornucopia.Game.find(game.id)
       assert updated_game.started_at != nil
+      
+      # Verify cards were dealt to all players via transaction
+      player1_cards = Cornucopia.list_player_cards(player1.id)
+      player2_cards = Cornucopia.list_player_cards(player2.id)
+      player3_cards = Cornucopia.list_player_cards(player3.id)
+      
+      # Each player should have cards
+      assert length(player1_cards) > 0
+      assert length(player2_cards) > 0
+      assert length(player3_cards) > 0
+      
+      # Total cards should equal 52 (standard deck) distributed evenly
+      total_cards = length(player1_cards) + length(player2_cards) + length(player3_cards)
+      assert total_cards == 52
     end
 
     test "does not restart an already started game", %{conn: conn, game: game} do
@@ -85,5 +99,68 @@ defmodule CopiWeb.GameLive.ShowTest do
       {:ok, updated_game} = Cornucopia.Game.find(started_game.id)
       assert DateTime.compare(updated_game.started_at, original_time) == :eq
     end
+
+    test "transaction ensures atomic card dealing with 4 players", %{conn: conn, game: game} do
+      # Add 4 players to test round-robin distribution
+      {:ok, player1} = Cornucopia.create_player(%{name: "Player 1", game_id: game.id})
+      {:ok, player2} = Cornucopia.create_player(%{name: "Player 2", game_id: game.id})
+      {:ok, player3} = Cornucopia.create_player(%{name: "Player 3", game_id: game.id})
+      {:ok, player4} = Cornucopia.create_player(%{name: "Player 4", game_id: game.id})
+
+      {:ok, view, _html} = live(conn, "/games/#{game.id}")
+
+      # Start game
+      render_click(view, "start_game", %{})
+
+      # Verify game started
+      {:ok, updated_game} = Cornucopia.Game.find(game.id)
+      assert updated_game.started_at != nil
+
+      # Verify all 52 cards were dealt atomically
+      player1_cards = Cornucopia.list_player_cards(player1.id)
+      player2_cards = Cornucopia.list_player_cards(player2.id)
+      player3_cards = Cornucopia.list_player_cards(player3.id)
+      player4_cards = Cornucopia.list_player_cards(player4.id)
+
+      # Each player should get 13 cards (52 / 4)
+      assert length(player1_cards) == 13
+      assert length(player2_cards) == 13
+      assert length(player3_cards) == 13
+      assert length(player4_cards) == 13
+
+      # Verify game update broadcast happened (started_at is set)
+      assert updated_game.started_at != nil
+    end
+
+    test "transaction with 5 players distributes cards evenly", %{conn: conn, game: game} do
+      # Add 5 players
+      {:ok, player1} = Cornucopia.create_player(%{name: "Player 1", game_id: game.id})
+      {:ok, player2} = Cornucopia.create_player(%{name: "Player 2", game_id: game.id})
+      {:ok, player3} = Cornucopia.create_player(%{name: "Player 3", game_id: game.id})
+      {:ok, player4} = Cornucopia.create_player(%{name: "Player 4", game_id: game.id})
+      {:ok, player5} = Cornucopia.create_player(%{name: "Player 5", game_id: game.id})
+
+      {:ok, view, _html} = live(conn, "/games/#{game.id}")
+      render_click(view, "start_game", %{})
+
+      # Verify cards distributed via transaction
+      player1_cards = Cornucopia.list_player_cards(player1.id)
+      player2_cards = Cornucopia.list_player_cards(player2.id)
+      player3_cards = Cornucopia.list_player_cards(player3.id)
+      player4_cards = Cornucopia.list_player_cards(player4.id)
+      player5_cards = Cornucopia.list_player_cards(player5.id)
+
+      # With 5 players, first 2 players get 11 cards, last 3 get 10 (52 cards total)
+      total = length(player1_cards) + length(player2_cards) + length(player3_cards) + 
+              length(player4_cards) + length(player5_cards)
+      assert total == 52
+      
+      # All players should have at least 10 cards
+      assert length(player1_cards) >= 10
+      assert length(player2_cards) >= 10
+      assert length(player3_cards) >= 10
+      assert length(player4_cards) >= 10
+      assert length(player5_cards) >= 10
+    end
   end
 end