PkmnLib.NET/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Moves/MementoTests.cs

using PkmnLib.Dynamic.Events;
using PkmnLib.Dynamic.Models;
using PkmnLib.Plugin.Gen7.Scripts.Moves;
using PkmnLib.Static;

namespace PkmnLib.Plugin.Gen7.Tests.Scripts.Moves;

/// <summary>
/// Tests for the <see cref="Memento"/> move script.
/// Gen VII Bulbapedia behavior: "Memento causes the user to faint and in return lowers the Attack and
/// Special Attack stat of the target by two stages each." From Generation V onward the user does not faint
/// if the move fails (no target, miss, blocked by a substitute) - that part is engine behavior, since
/// <see cref="Memento.OnSecondaryEffect"/> only runs when the move successfully hits.
/// </summary>
public class MementoTests
{
    private static (Memento script, IExecutingMove move, IBattlePokemon target, IBattlePokemon user) CreateTestSetup()
    {
        var script = new Memento();
        var move = Substitute.For<IExecutingMove>();
        var target = Substitute.For<IBattlePokemon>();
        var user = Substitute.For<IBattlePokemon>();
        move.User.Returns(user);
        return (script, move, target, user);
    }

    /// <summary>
    /// Helper to extract the arguments of the received ChangeStatBoost call for the given stat, or null
    /// when no boost for that stat was requested. Received-call inspection is used instead of NSubstitute
    /// argument matchers because the trailing <see cref="EventBatchId"/> parameter cannot be bound by
    /// <c>Arg.Any</c>.
    /// </summary>
    private static object?[]? GetStatBoostArgs(IBattlePokemon pokemon, Statistic stat) =>
        pokemon.ReceivedCalls().Where(c => c.GetMethodInfo().Name == "ChangeStatBoost").Select(c => c.GetArguments())
            .FirstOrDefault(args => (Statistic)args[0]! == stat);

    /// <summary>
    /// Bulbapedia: "Memento causes the user to faint and in return lowers the Attack and Special Attack stat
    /// of the target by two stages each."
    /// The Attack drop is caused by the opponent's move, so it is not self-inflicted and not forced.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_Hit_LowersTargetAttackByTwoStages()
    {
        // Arrange
        var (script, move, target, _) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var args = GetStatBoostArgs(target, Statistic.Attack);
        await Assert.That(args).IsNotNull();
        await Assert.That((sbyte)args![1]!).IsEqualTo((sbyte)-2);
        await Assert.That((bool)args[2]!).IsFalse();
        await Assert.That((bool)args[3]!).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: "Memento causes the user to faint and in return lowers the Attack and Special Attack stat
    /// of the target by two stages each."
    /// The Special Attack drop is caused by the opponent's move, so it is not self-inflicted and not forced.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_Hit_LowersTargetSpecialAttackByTwoStages()
    {
        // Arrange
        var (script, move, target, _) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var args = GetStatBoostArgs(target, Statistic.SpecialAttack);
        await Assert.That(args).IsNotNull();
        await Assert.That((sbyte)args![1]!).IsEqualTo((sbyte)-2);
        await Assert.That((bool)args[2]!).IsFalse();
        await Assert.That((bool)args[3]!).IsFalse();
    }

    /// <summary>
    /// Bulbapedia: "Memento causes the user to faint and in return lowers the Attack and Special Attack stat
    /// of the target by two stages each."
    /// Only those two stats are lowered; no other stat changes are requested.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_Hit_OnlyLowersAttackAndSpecialAttack()
    {
        // Arrange
        var (script, move, target, _) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var statBoostCalls = target.ReceivedCalls().Count(c => c.GetMethodInfo().Name == "ChangeStatBoost");
        await Assert.That(statBoostCalls).IsEqualTo(2);
    }

    /// <summary>
    /// Bulbapedia: "Memento causes the user to faint".
    /// The faint is not move damage, so it uses <see cref="DamageSource.Misc"/>.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_Hit_UserFaints()
    {
        // Arrange
        var (script, move, target, user) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var faintCall = user.ReceivedCalls().FirstOrDefault(c => c.GetMethodInfo().Name == "Faint");
        await Assert.That(faintCall).IsNotNull();
        await Assert.That((DamageSource)faintCall!.GetArguments()[0]!).IsEqualTo(DamageSource.Misc);
    }

    /// <summary>
    /// Bulbapedia (Generation V onward): "the user faints if it successfully hits but cannot lower stats due
    /// to abilities like Clear Body or stats already at -6."
    /// A substitute's <see cref="IBattlePokemon.ChangeStatBoost"/> returns false by default (the stat drops were
    /// prevented), but the user must still faint.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_StatDropsPrevented_UserStillFaints()
    {
        // Arrange
        var (script, move, target, user) = CreateTestSetup();

        // Act - the unconfigured ChangeStatBoost calls return false, as if blocked by Clear Body
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        await Assert.That(user.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Faint")).IsTrue();
    }

    /// <summary>
    /// Technical test: both stat drops are batched under the same <see cref="EventBatchId"/> so they are
    /// shown as a single event to the client.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_Hit_StatDropsShareEventBatch()
    {
        // Arrange
        var (script, move, target, _) = CreateTestSetup();

        // Act
        script.OnSecondaryEffect(move, target, 0);

        // Assert
        var attackBatch = (EventBatchId)GetStatBoostArgs(target, Statistic.Attack)![4]!;
        var specialAttackBatch = (EventBatchId)GetStatBoostArgs(target, Statistic.SpecialAttack)![4]!;
        await Assert.That(attackBatch).IsEqualTo(specialAttackBatch);
    }
}