minesweeper-codex/tests/Minesweeper.Tests/MinesweeperGameTests.cs

using Minesweeper.Game;
using Xunit;

namespace Minesweeper.Tests;

public class MinesweeperGameTests
{
    private static readonly string[] s_twinMineLayout =
    [
        "x.x",
        "...",
        "...",
    ];

    private static readonly string[] s_cornerMineLayout =
    [
        "x..",
        "...",
        "...",
    ];

    [Fact]
    public void TheFirstClickPlantsMinesAndIsSafe()
    {
        var board = new Board(9, 9, 10);
        var game = new MinesweeperGame(board, new Random(7));

        Assert.False(game.HasOpenedFirstCell);
        var result = game.Open(new CellRef(4, 4));

        Assert.True(board.MinesPlanted);
        Assert.True(game.HasOpenedFirstCell);
        Assert.False(result.HitMine);
        Assert.True(result.Opened.Count > 1, "the default safe zone should open an area");
        Assert.Equal(GameStatus.Playing, game.Status);
    }

    [Fact]
    public void EverySafeSquareOpeningWinsAndFlagsTheMines()
    {
        var game = TestBoards.Game(1, s_cornerMineLayout);
        var result = game.Open(new CellRef(2, 0));

        Assert.Equal(8, result.Opened.Count);
        Assert.Equal(GameStatus.Won, game.Status);
        Assert.Equal(1, game.FlagsPlaced);
        Assert.Equal(0, game.MinesRemaining);
        Assert.All(game.Board.MineCells(), mine => Assert.True(game.Board.At(mine).IsFlagged));
    }

    [Fact]
    public void SteppingOnAMineEndsTheRoundAndShowsTheBoard()
    {
        var game = TestBoards.SingleMine(4, 4);
        game.ToggleFlag(new CellRef(3, 3));

        var result = game.Open(new CellRef(0, 0));

        Assert.True(result.HitMine);
        Assert.Equal(GameStatus.Lost, game.Status);
        Assert.Equal(new CellRef(0, 0), game.Explosion!.Value);
        Assert.True(game.Board.At(0, 0).Exploded);
        Assert.All(game.Board.MineCells(), mine => Assert.True(game.Board.At(mine).IsRevealed || game.Board.At(mine).IsFlagged));

        // A flag on safe ground stays put so the renderer can mark it as wrong.
        Assert.True(game.Board.At(3, 3).IsFlagged);
        Assert.False(game.Board.At(3, 3).IsMine);
    }

    [Fact]
    public void FinishedRoundsIgnoreFurtherMoves()
    {
        var game = TestBoards.SingleMine();
        game.Open(new CellRef(0, 0));
        var revealed = game.RevealedCount;

        Assert.False(game.Open(new CellRef(2, 2)).AnyOpened);
        Assert.False(game.ToggleFlag(new CellRef(2, 3)));
        Assert.Equal(revealed, game.RevealedCount);
    }

    [Fact]
    public void FlagsMoveTheCounterBothWays()
    {
        var game = TestBoards.SingleMine();
        Assert.Equal(1, game.MinesRemaining);

        Assert.True(game.ToggleFlag(new CellRef(1, 1)));
        Assert.Equal(0, game.MinesRemaining);

        Assert.True(game.ToggleFlag(new CellRef(2, 2)));
        Assert.Equal(-1, game.MinesRemaining);

        Assert.True(game.ToggleFlag(new CellRef(1, 1)));
        Assert.Equal(0, game.MinesRemaining);
        Assert.True(game.ToggleFlag(new CellRef(1, 1)), "a cleared square can be flagged again");
        Assert.Equal(-1, game.MinesRemaining);
    }

    [Fact]
    public void FlaggedSquaresCannotBeOpened()
    {
        var game = TestBoards.SingleMine();
        game.ToggleFlag(new CellRef(1, 1));

        Assert.False(game.Open(new CellRef(1, 1)).AnyOpened);
        Assert.True(game.Board.At(1, 1).IsFlagged);
    }

    [Fact]
    public void QuestionMarksAreOptionalAndStayOpenable()
    {
        var game = TestBoards.SingleMine();

        Assert.False(game.ToggleQuestion(new CellRef(1, 1), questionMarksEnabled: false));

        Assert.True(game.ToggleQuestion(new CellRef(1, 1), questionMarksEnabled: true));
        Assert.Equal(CellState.Question, game.Board.At(1, 1).State);

        Assert.True(game.Open(new CellRef(1, 1)).AnyOpened);
        Assert.True(game.Board.At(1, 1).IsRevealed);
    }

    [Fact]
    public void ChordingThroughTheGameCountsTheNewSquares()
    {
        var game = TestBoards.Game(1, s_twinMineLayout);
        game.Open(new CellRef(1, 0));
        game.ToggleFlag(new CellRef(0, 0));
        game.ToggleFlag(new CellRef(2, 0));

        var result = game.Chord(new CellRef(1, 0));

        Assert.Equal(3, result.Opened.Count);
        Assert.Equal(4, game.RevealedCount);
        Assert.Equal(GameStatus.Playing, game.Status);
    }

    [Fact]
    public void RevealSolutionOnlyWorksAfterTheRound()
    {
        var game = TestBoards.SingleMine();
        game.RevealSolution();

        Assert.False(game.Board.At(0, 0).IsRevealed);

        game.Open(new CellRef(0, 0));
        game.RevealSolution();

        Assert.True(game.Board.At(0, 0).IsRevealed);
    }
}