Fix bug in stat reducing not functioning properly

PkmnLib.Static/StatisticSet.cs

@@ -312,7 +312,7 @@ public abstract record ClampedStatisticSet<T> : StatisticSet<T> where T : struct
         var current = GetStatistic(stat);
         var newValue = Subtract(current, value);
         if (newValue.CompareTo(Min) < 0)
-            value = Add(Min, current);
+            value = Subtract(current, Min);
         if (value.CompareTo(default) == 0)
             return false;
         return base.DecreaseStatistic(stat, value);

PkmnLib.Tests/Dynamic/PokemonStatBoostTests.cs

@@ -0,0 +1,105 @@
+using PkmnLib.Dynamic.Libraries;
+using PkmnLib.Dynamic.Models;
+using PkmnLib.Static;
+using PkmnLib.Static.Species;
+using PkmnLib.Tests.Integration;
+
+namespace PkmnLib.Tests.Dynamic;
+
+public class PokemonStatBoostTests
+{
+    private static IPokemon CreatePokemon()
+    {
+        var library = LibraryHelpers.LoadLibrary();
+        if (!library.StaticLibrary.Species.TryGet("bulbasaur", out var species))
+            throw new InvalidOperationException("Failed to load bulbasaur species.");
+        return new PokemonImpl(library, species!, species!.GetDefaultForm(), new AbilityIndex
+        {
+            Index = 0,
+            IsHidden = false,
+        }, 50, 0, Gender.Male, 0, "hardy");
+    }
+
+    [Test]
+    public async Task ChangeStatBoost_IncreasesStatBoost()
+    {
+        var pokemon = CreatePokemon();
+
+        var changed = pokemon.ChangeStatBoost(Statistic.Attack, 2, true, false);
+
+        await Assert.That(changed).IsTrue();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo((sbyte)2);
+    }
+
+    [Test]
+    public async Task ChangeStatBoost_DecreasesStatBoost()
+    {
+        var pokemon = CreatePokemon();
+
+        var changed = pokemon.ChangeStatBoost(Statistic.Attack, -2, true, false);
+
+        await Assert.That(changed).IsTrue();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo((sbyte)-2);
+    }
+
+    [Test]
+    public async Task ChangeStatBoost_ReturnsFalseWhenChangeIsZero()
+    {
+        var pokemon = CreatePokemon();
+
+        var changed = pokemon.ChangeStatBoost(Statistic.Attack, 0, true, false);
+
+        await Assert.That(changed).IsFalse();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo((sbyte)0);
+    }
+
+    [Test]
+    public async Task ChangeStatBoost_ReturnsFalseWhenMaxCapReached()
+    {
+        var pokemon = CreatePokemon();
+
+        // Raise the stat boost all the way to the maximum of +6.
+        var raised = pokemon.ChangeStatBoost(Statistic.Attack, StatBoostStatisticSet.MaxStatBoost, true, false);
+        await Assert.That(raised).IsTrue();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo(StatBoostStatisticSet.MaxStatBoost);
+
+        // The cap has been reached, so a further increase should do nothing and report failure.
+        var changed = pokemon.ChangeStatBoost(Statistic.Attack, 1, true, false);
+
+        await Assert.That(changed).IsFalse();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo(StatBoostStatisticSet.MaxStatBoost);
+    }
+
+    [Test]
+    public async Task ChangeStatBoost_ReturnsFalseWhenMinCapReached()
+    {
+        var pokemon = CreatePokemon();
+
+        // Lower the stat boost all the way to the minimum of -6.
+        var lowered = pokemon.ChangeStatBoost(Statistic.Attack, StatBoostStatisticSet.MinStatBoost, true, false);
+        await Assert.That(lowered).IsTrue();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo(StatBoostStatisticSet.MinStatBoost);
+
+        // The floor has been reached, so a further decrease should do nothing and report failure.
+        var changed = pokemon.ChangeStatBoost(Statistic.Attack, -1, true, false);
+
+        await Assert.That(changed).IsFalse();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo(StatBoostStatisticSet.MinStatBoost);
+    }
+
+    [Test]
+    public async Task ChangeStatBoost_ClampsToCapButStillReportsChangeWhenPartiallyApplied()
+    {
+        var pokemon = CreatePokemon();
+
+        // Raise to +5, one below the cap.
+        await Assert.That(pokemon.ChangeStatBoost(Statistic.Attack, 5, true, false)).IsTrue();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo((sbyte)5);
+
+        // Asking for +4 can only apply +1 before hitting the cap. Since a change is still made, it reports success.
+        var changed = pokemon.ChangeStatBoost(Statistic.Attack, 4, true, false);
+
+        await Assert.That(changed).IsTrue();
+        await Assert.That(pokemon.StatBoost.Attack).IsEqualTo(StatBoostStatisticSet.MaxStatBoost);
+    }
+}