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

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

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

/// <summary>
/// Tests for the <see cref="KnockOff"/> move script.
/// Behavior is verified against the Bulbapedia page for Knock Off (Generation VII).
/// </summary>
public class KnockOffTests
{
    /// <summary>
    /// Creates a fully mocked test setup for Knock Off tests. When <paramref name="targetHasItem"/> is true,
    /// <see cref="IPokemon.TryStealHeldItem"/> succeeds and yields a mocked item.
    /// </summary>
    private static (KnockOff script, IExecutingMove move, IPokemon target, IPokemon user, IHitData hitData)
        CreateTestSetup(bool targetHasItem)
    {
        var script = new KnockOff();
        var move = Substitute.For<IExecutingMove>();
        var target = Substitute.For<IPokemon>();
        var hitData = Substitute.For<IHitData>();
        move.GetHitData(target, 0).Returns(hitData);

        target.TryStealHeldItem(out Arg.Any<IItem?>()).Returns(callInfo =>
        {
            callInfo[0] = targetHasItem ? Substitute.For<IItem>() : null;
            return targetHasItem;
        });

        var user = Substitute.For<IPokemon>();
        move.User.Returns(user);

        return (script, move, target, user, hitData);
    }

    /// <summary>
    /// Bulbapedia: "Knock Off inflicts damage and knocks off the target's held item if it has one."
    /// (Generation V onwards: "Knock Off now removes the held item rather than rendering it unusable".)
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetHoldsItem_ItemIsRemoved()
    {
        // Arrange
        var (script, move, target, _, hitData) = CreateTestSetup(true);

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

        // Assert
        target.Received(1).TryStealHeldItem(out Arg.Any<IItem?>());
        hitData.DidNotReceive().Fail();
        await Assert.That(target.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "TryStealHeldItem")).IsTrue();
    }

    /// <summary>
    /// Bulbapedia: "Knock Off inflicts damage and knocks off the target's held item if it has one."
    /// Against a target without a held item the move simply deals its damage without any further effect; it
    /// does not fail.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_TargetHoldsNoItem_HitIsNotMarkedAsFailed()
    {
        // Arrange
        var (script, move, target, _, hitData) = CreateTestSetup(false);

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

        // Assert
        hitData.DidNotReceive().Fail();
        await Assert.That(hitData.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Fail")).IsFalse();
    }

    /// <summary>
    /// Bulbapedia (Generation V onwards): "If the user faints due to the target's Ability (Rough Skin or
    /// Iron Barbs) or held Rocky Helmet, it cannot remove the target's held item."
    /// Those effects damage the user before the secondary effect runs, so a user that has fainted by then must
    /// not remove the item.
    /// </summary>
    [Test]
    public async Task OnSecondaryEffect_UserIsFainted_ItemIsNotRemoved()
    {
        // Arrange
        var (script, move, target, user, _) = CreateTestSetup(true);
        user.IsFainted.Returns(true);

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

        // Assert
        await Assert.That(target.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "TryStealHeldItem")).IsFalse();
    }

    /// <summary>
    /// Bulbapedia (Generation VI onwards): "If Knock Off is used on a Pokémon that is holding an item that can
    /// be knocked off, its base power will be boosted by 50%."
    /// With Knock Off's base power of 65 the boosted power is 97 (65 × 1.5, fractions dropped).
    /// </summary>
    [Test]
    public async Task ChangeBasePower_TargetHoldsRemovableItem_BasePowerBoostedByFiftyPercent()
    {
        // Arrange
        var (script, move, target, _, _) = CreateTestSetup(true);
        target.HeldItem.Returns(Substitute.For<IItem>());
        ushort basePower = 65;

        // Act
        ((IScriptChangeBasePower)script).ChangeBasePower(move, target, 0, ref basePower);

        // Assert
        await Assert.That(basePower).IsEqualTo((ushort)97);
    }

    /// <summary>
    /// Bulbapedia (Generation VI onwards): "If Knock Off is used on a Pokémon that is holding an item that can
    /// be knocked off, its base power will be boosted by 50%."
    /// A target without a held item does not grant the boost, so the base power stays unchanged.
    /// </summary>
    [Test]
    public async Task ChangeBasePower_TargetHoldsNoItem_BasePowerUnchanged()
    {
        // Arrange
        var (script, move, target, _, _) = CreateTestSetup(false);
        target.HeldItem.Returns((IItem?)null);
        ushort basePower = 65;

        // Act
        ((IScriptChangeBasePower)script).ChangeBasePower(move, target, 0, ref basePower);

        // Assert
        await Assert.That(basePower).IsEqualTo((ushort)65);
    }
}