oecs-sharp/Game.TicTacToe.Tests/SnapshotTests.cs

using FluentAssertions;
using Game.TicTacToe;
using OECS;
using OECS.PlayTest;
using Xunit;
using Xunit.Abstractions;

namespace Game.TicTacToe.Tests;

/// <summary>
/// Baseline snapshot and log tests for TicTacToe.
/// Captures the world state as text and R3 change logs so they can be
/// reviewed manually and compared across changes.
/// </summary>
public class SnapshotTests
{
    private readonly ITestOutputHelper _output;

    public SnapshotTests(ITestOutputHelper output)
    {
        _output = output;
    }

    [Fact]
    public void Snapshot_InitialBoard()
    {
        var world = new World();
        for (int r = 0; r < 3; r++)
            for (int c = 0; c < 3; c++)
                world.AddComponent(world.CreateEntity(), new Cell { Row = r, Col = c });

        world.SetSingleton(new GameState
        {
            CurrentPlayer = Player.X,
            Status = GameStatus.Playing,
            MoveCount = 0
        });

        var snapshot = TestHelpers.SnapshotWorld(world);
        _output.WriteLine(snapshot);

        snapshot.Should().Contain("GameState: X's turn, 0 moves");
        snapshot.Should().Contain("Cells: 9 total, 0 marked");
    }

    [Fact]
    public void Snapshot_AfterThreeMoves()
    {
        var (world, group) = TestHelpers.SetupGame();

        TestHelpers.PlayMoves(world, group, (0, 0), (1, 1), (2, 2));

        var snapshot = TestHelpers.SnapshotWorld(world);
        _output.WriteLine(snapshot);

        snapshot.Should().Contain("GameState: O's turn, 3 moves");
        snapshot.Should().Contain("Cells: 9 total, 3 marked");
        snapshot.Should().Contain("(0,0): X");
        snapshot.Should().Contain("(1,1): O");
        snapshot.Should().Contain("(2,2): X");
    }

    [Fact]
    public void Snapshot_XWins()
    {
        var (world, group) = TestHelpers.SetupGame();

        TestHelpers.PlayMoves(world, group, (0, 0), (1, 0), (0, 1), (1, 1), (0, 2));

        var snapshot = TestHelpers.SnapshotWorld(world);
        _output.WriteLine(snapshot);

        snapshot.Should().Contain("GameState: XWon");
        snapshot.Should().Contain("Cells: 9 total, 5 marked");
    }

    [Fact]
    public void Snapshot_Draw()
    {
        var (world, group) = TestHelpers.SetupGame();

        TestHelpers.PlayMoves(world, group,
            (0, 0), (0, 1), (0, 2),
            (1, 1), (1, 0), (1, 2),
            (2, 1), (2, 0), (2, 2));

        var snapshot = TestHelpers.SnapshotWorld(world);
        _output.WriteLine(snapshot);

        snapshot.Should().Contain("GameState: Draw");
        snapshot.Should().Contain("Cells: 9 total, 9 marked");
    }

    [Fact]
    public void Log_ReactivityDuringGame()
    {
        var (world, group) = TestHelpers.SetupGame();

        using var capture = new ObservableCapture(world);
        capture.FormatWith<Mark>(m => m.Player.ToString());
        capture.FormatWith<GameState>(s => $"{s.Status} ({s.CurrentPlayer}, {s.MoveCount} moves)");

        TestHelpers.PlayMoves(world, group, (0, 0), (1, 0), (0, 1), (1, 1), (0, 2));

        var logText = string.Join("\n", capture.GetLogLines());
        _output.WriteLine(logText);

        capture.GetLogLines().Should().Contain(l => l.Contains("ComponentAdded") && l.Contains("Mark"));
        capture.GetLogLines().Should().Contain(l => l.Contains("ComponentModified") && l.Contains("GameState"));
    }

    [Fact]
    public void Serialization_RoundTrip_PreservesSnapshot()
    {
        var (world, group) = TestHelpers.SetupGame();

        TestHelpers.PlayMoves(world, group, (0, 0), (1, 1), (2, 2));

        var before = TestHelpers.SnapshotWorld(world);

        using var stream = new MemoryStream();
        WorldSerializer.Save(world, stream);
        stream.Position = 0;

        var world2 = new World();
        WorldSerializer.Load(world2, stream);

        var after = TestHelpers.SnapshotWorld(world2);

        _output.WriteLine("=== Before ===");
        _output.WriteLine(before);
        _output.WriteLine("=== After ===");
        _output.WriteLine(after);

        after.Should().Be(before);
    }
}