zfxaction26_1/tests/SideScrollerGame.Sim.Tests/SimulationReplayTests.cs

using System.Collections.Immutable;
using SideScrollerGame.Sim.Input;
using SideScrollerGame.Sim.Replay;
using SideScrollerGame.Sim.Serialization;

namespace SideScrollerGame.Sim.Tests;

public sealed class SimulationReplayTests
{
    [Fact]
    public void SameSeedAndActions_ProduceSameHashes()
    {
        var definition = SimulationTestFactory.CreateGameDefinition();
        var config = SimulationTestFactory.CreateConfig();
        TickActionBatch[] batches =
        [
            SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 1, 0)),
            SimulationTestFactory.CreateTick(2, new AimAxisChanged(new(1), 3, 4)),
            SimulationTestFactory.CreateTick(3, new ButtonChanged(new(1), InputButton.Dash, true))
        ];

        Simulation left = new(definition, config, 42);
        Simulation right = new(definition, config, 42);

        var leftHashes = ImmutableArray.CreateBuilder<int>();
        var rightHashes = ImmutableArray.CreateBuilder<int>();
        foreach (var batch in batches)
        {
            leftHashes.Add(left.Step(batch).StateHash);
            rightHashes.Add(right.Step(batch).StateHash);
        }

        Assert.Equal(leftHashes.ToImmutable(), rightHashes.ToImmutable());
    }

    [Fact]
    public void DifferentSeeds_ProduceDifferentHashes()
    {
        var definition = SimulationTestFactory.CreateGameDefinition();
        var config = SimulationTestFactory.CreateConfig();
        var batch = TickActionBatch.Empty(1);

        Simulation left = new(definition, config, 1);
        Simulation right = new(definition, config, 2);

        Assert.NotEqual(left.Step(batch).StateHash, right.Step(batch).StateHash);
    }

    [Fact]
    public void ReplayRecord_RoundTripsAndReplaysExpectedHashes()
    {
        var definition = SimulationTestFactory.CreateGameDefinition();
        var config = SimulationTestFactory.CreateConfig();
        Simulation simulation = new(definition, config, 9);
        ReplayRecorder recorder = new();

        TickActionBatch[] batches =
        [
            SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 2, 0), new AimAxisChanged(new(1), 5, 6)),
            SimulationTestFactory.CreateTick(2, new ButtonChanged(new(1), InputButton.FireSecondary, true)),
            SimulationTestFactory.CreateTick(3, new WeaponSlotSelected(new(1), 4))
        ];

        foreach (var batch in batches)
        {
            var result = simulation.Step(batch);
            recorder.Append(batch, result);
        }

        var replay = recorder.Build(definition, config, 9);
        var payload = ReplayRecordSerializer.Serialize(replay);
        var loadedReplay = ReplayRecordSerializer.Deserialize(payload);
        var replayedHashes = ReplayPlayer.Play(loadedReplay, definition, config);

        Assert.Equal(loadedReplay.Ticks.Select(static tick => tick.ExpectedStateHash).ToImmutableArray(), replayedHashes);
    }

    [Fact]
    public void ReplayPlayer_RejectsMismatchedDefinition()
    {
        var config = SimulationTestFactory.CreateConfig();
        var definition = SimulationTestFactory.CreateGameDefinition();
        ReplayRecord replay = new(123, 9, config.TicksPerSecond, ImmutableArray<RecordedTick>.Empty);

        var exception = Assert.Throws<InvalidOperationException>(() => ReplayPlayer.Play(replay, definition, config));

        Assert.Contains("content hash", exception.Message.ToLowerInvariant());
    }

    [Fact]
    public void ReplayPlayer_RejectsMismatchedTickRate()
    {
        var definition = SimulationTestFactory.CreateGameDefinition();
        var replay = new ReplayRecorder().Build(definition, SimulationTestFactory.CreateConfig(), 9) with { TicksPerSecond = 30 };

        var exception = Assert.Throws<InvalidOperationException>(() => ReplayPlayer.Play(replay, definition, SimulationTestFactory.CreateConfig()));

        Assert.Contains("tick rate", exception.Message.ToLowerInvariant());
    }

    [Fact]
    public void ReplayPlayer_RejectsDivergentHashes()
    {
        var definition = SimulationTestFactory.CreateGameDefinition();
        var config = SimulationTestFactory.CreateConfig();
        Simulation simulation = new(definition, config, 55);
        ReplayRecorder recorder = new();
        var batch = SimulationTestFactory.CreateTick(1, new MoveAxisChanged(new(1), 1, 0));
        var result = simulation.Step(batch);
        recorder.Append(batch, result);

        var replay = recorder.Build(definition, config, 55);
        var divergentReplay = replay with { Ticks = ImmutableArray.Create(replay.Ticks[0] with { ExpectedStateHash = replay.Ticks[0].ExpectedStateHash + 1 }) };

        var exception = Assert.Throws<InvalidOperationException>(() => ReplayPlayer.Play(divergentReplay, definition, config));

        Assert.Contains("diverged", exception.Message.ToLowerInvariant());
    }
}