🧪 Created failed test to verify the bug

PokemonAdventureGame.Tests/PokemonAdventureGame.Tests/Battles/BattleTestUtils.cs

@@ -0,0 +1,44 @@
+using PokemonAdventureGame.Interfaces;
+using PokemonAdventureGame.Pokemon;
+using PokemonAdventureGame.PokemonTeam;
+using System.Linq;
+using Xunit;
+
+namespace PokemonAdventureGame.Tests.Battles
+{
+    public static class BattleTestUtils
+    {
+        public static void FaintPokemon<TPokemon>(ITrainer trainer)
+            where TPokemon : IPokemon
+        {
+            TrainerPokemon pokemon = trainer.PokemonTeam.FirstOrDefault(x => x.Pokemon is Gyarados);
+            FaintSpecificPokemon(pokemon);
+        }
+
+        public static void FaintSpecificPokemon(TrainerPokemon pokemon)
+        {
+            pokemon.Pokemon.ReceiveDamage(9999);
+            pokemon.SetAsFainted();
+        }
+
+        public static IPokemon GetCurrentPokemonForBattle(ITrainer trainer)
+        {
+            // This will set the "Current" property to true for the first available Pokemon.
+            _ = trainer.GetNextAvailablePokemon();
+
+            // This will return the Pokemon that will be used in the battle.
+            // NOTE: This might return a different instance of the Pokemon
+            // than "GetNextAvailablePokemon" when multiple of the same are in the team.
+            return trainer.GetCurrentPokemon();
+        }
+
+        public static void AssertPokemonAndNotFainted<TPokemon>(IPokemon pokemon)
+            where TPokemon : IPokemon
+        {
+            //string pokemonName = typeof(TPokemon).Name;
+            //Assert.Equal(pokemonName, pokemon?.GetType().Name);
+            Assert.False(pokemon.HasFainted());
+            Assert.IsType<TPokemon>(pokemon);
+        }
+    }
+}

PokemonAdventureGame.Tests/PokemonAdventureGame.Tests/Battles/LanceBattleTests.cs

@@ -0,0 +1,76 @@
+using PokemonAdventureGame.Factories;
+using PokemonAdventureGame.Interfaces;
+using PokemonAdventureGame.Pokemon;
+using PokemonAdventureGame.PokemonTeam;
+using PokemonAdventureGame.Trainers;
+using System.Linq;
+using Xunit;
+
+namespace PokemonAdventureGame.Tests.Battles
+{
+    public class LanceBattleTests
+    {
+        [Fact]
+        public void LanceFirstPokemon()
+        {
+            ITrainer trainer = TrainerFactory.CreateTrainer<Lance>();
+
+            IPokemon currentPokemon = BattleTestUtils.GetCurrentPokemonForBattle(trainer);
+
+            BattleTestUtils.AssertPokemonAndNotFainted<Gyarados>(currentPokemon);
+        }
+
+        [Fact]
+        public void LanceSecondPokemon()
+        {
+            ITrainer trainer = TrainerFactory.CreateTrainer<Lance>();
+
+            // Simulate Gyarados fainting
+            TrainerPokemon gyarados = trainer.PokemonTeam.FirstOrDefault(x => x.Pokemon is Gyarados);
+            gyarados.Fainted = true;
+
+            // Check next Pokemon is Dragonite
+            IPokemon currentPokemon = BattleTestUtils.GetCurrentPokemonForBattle(trainer);
+
+            BattleTestUtils.AssertPokemonAndNotFainted<Dragonite>(currentPokemon);
+        }
+
+        [Fact]
+        public void LanceThirdPokemon()
+        {
+            ITrainer trainer = TrainerFactory.CreateTrainer<Lance>();
+
+            // Simulate Gyarados fainting
+            BattleTestUtils.FaintPokemon<Gyarados>(trainer);
+
+            // Simulate first Dragonite fainting
+            TrainerPokemon firstDragonite = trainer.PokemonTeam.FirstOrDefault(x => x.Pokemon is Dragonite);
+            BattleTestUtils.FaintSpecificPokemon(firstDragonite);
+
+            // Check next Pokemon is Dragonite
+            IPokemon currentPokemon = BattleTestUtils.GetCurrentPokemonForBattle(trainer);
+
+            BattleTestUtils.AssertPokemonAndNotFainted<Dragonite>(currentPokemon);
+        }
+
+        [Fact]
+        public void LanceAllDragoniteDown()
+        {
+            ITrainer trainer = TrainerFactory.CreateTrainer<Lance>();
+
+            // Simulate Gyarados fainting
+            BattleTestUtils.FaintPokemon<Gyarados>(trainer);
+
+            // Simulate all Dragonites fainting
+            trainer.PokemonTeam
+                .Where(x => x.Pokemon is Dragonite)
+                .ToList()
+                .ForEach(x => BattleTestUtils.FaintSpecificPokemon(x));
+
+            // Check next Pokemon is Dragonite
+            IPokemon currentPokemon = BattleTestUtils.GetCurrentPokemonForBattle(trainer);
+
+            BattleTestUtils.AssertPokemonAndNotFainted<Aerodactyl>(currentPokemon);
+        }
+    }
+}