battle-royal-tetris/server/__tests__/game-logic.test.js

// Unit tests for pure game logic functions

const {
  BOARD_WIDTH,
  BOARD_HEIGHT,
  GARBAGE_COLOR,
  createEmptyBoard,
  getPieceFromType,
  isValidPosition,
  getGhostY,
  checkBoardOverflow,
  addGarbageRow,
  lockPieceToBoard,
  clearRows,
  generatePieceBag,
  createPieceQueue
} = require('../game-logic');

describe('createEmptyBoard', () => {
  test('creates a 20x10 board', () => {
    const board = createEmptyBoard();
    expect(board.length).toBe(BOARD_HEIGHT);
    expect(board[0].length).toBe(BOARD_WIDTH);
  });

  test('all cells are initialized to 0', () => {
    const board = createEmptyBoard();
    for (let row = 0; row < BOARD_HEIGHT; row++) {
      for (let col = 0; col < BOARD_WIDTH; col++) {
        expect(board[row][col]).toBe(0);
      }
    }
  });
});

describe('getPieceFromType', () => {
  test('returns correct piece for I tetromino', () => {
    const piece = getPieceFromType('I');
    expect(piece.type).toBe('I');
    expect(piece.color).toBe('#00ffff');
    expect(piece.y).toBe(0);
  });

  test('returns correct piece for O tetromino', () => {
    const piece = getPieceFromType('O');
    expect(piece.type).toBe('O');
    expect(piece.color).toBe('#ffff00');
  });

  test('centers piece horizontally', () => {
    const piece = getPieceFromType('I');
    expect(piece.x).toBe(Math.floor(BOARD_WIDTH / 2) - Math.floor(4 / 2));
  });
});

describe('isValidPosition', () => {
  test('returns true for valid position', () => {
    const board = createEmptyBoard();
    const piece = getPieceFromType('I');
    expect(isValidPosition(piece, 3, 5, board)).toBe(true);
  });

  test('returns false for position out of bounds (left)', () => {
    const board = createEmptyBoard();
    const piece = getPieceFromType('I');
    expect(isValidPosition(piece, -1, 5, board)).toBe(false);
  });

  test('returns false for position out of bounds (right)', () => {
    const board = createEmptyBoard();
    const piece = getPieceFromType('I');
    expect(isValidPosition(piece, 10, 5, board)).toBe(false);
  });

  test('returns false for position out of bounds (bottom)', () => {
    const board = createEmptyBoard();
    const piece = getPieceFromType('I');
    expect(isValidPosition(piece, 3, 20, board)).toBe(false);
  });

  test('returns false for collision with existing block', () => {
    const board = createEmptyBoard();
    board[10][5] = '#ff0000'; // Place a block
    const piece = getPieceFromType('O');
    expect(isValidPosition(piece, 4, 9, board)).toBe(false);
  });
});

describe('getGhostY', () => {
  test('returns null for no piece', () => {
    expect(getGhostY(null, createEmptyBoard())).toBe(null);
  });

  test('returns current Y when piece is at bottom', () => {
    const board = createEmptyBoard();
    const piece = { ...getPieceFromType('I'), y: 15 };
    const ghostY = getGhostY(piece, board);
    expect(ghostY).toBeLessThanOrEqual(19);
  });

  test('returns lower Y when piece can fall', () => {
    const board = createEmptyBoard();
    const piece = getPieceFromType('I');
    const ghostY = getGhostY(piece, board);
    expect(ghostY).toBeGreaterThan(piece.y);
  });
});

describe('checkBoardOverflow', () => {
  test('returns false for empty board', () => {
    const board = createEmptyBoard();
    expect(checkBoardOverflow(board)).toBe(false);
  });

  test('returns false when only bottom rows have blocks', () => {
    const board = createEmptyBoard();
    board[19][5] = '#ff0000';
    board[18][5] = '#ff0000';
    expect(checkBoardOverflow(board)).toBe(false);
  });

  test('returns true when row 0 has a block', () => {
    const board = createEmptyBoard();
    board[0][5] = '#ff0000';
    expect(checkBoardOverflow(board)).toBe(true);
  });

  test('returns true when row 1 has a block', () => {
    const board = createEmptyBoard();
    board[1][5] = '#ff0000';
    expect(checkBoardOverflow(board)).toBe(true);
  });

  test('returns false when only row 2 has blocks', () => {
    const board = createEmptyBoard();
    board[2][5] = '#ff0000';
    expect(checkBoardOverflow(board)).toBe(false);
  });
});

describe('addGarbageRow', () => {
  test('maintains board height', () => {
    const board = createEmptyBoard();
    const result = addGarbageRow(board, null);
    expect(result.board.length).toBe(BOARD_HEIGHT);
  });

  test('adds garbage row at bottom', () => {
    const board = createEmptyBoard();
    const result = addGarbageRow(board, null);
    const bottomRow = result.board[BOARD_HEIGHT - 1];
    expect(bottomRow.some(cell => cell === GARBAGE_COLOR)).toBe(true);
  });

  test('garbage row has exactly one gap', () => {
    const board = createEmptyBoard();
    const result = addGarbageRow(board, null);
    const bottomRow = result.board[BOARD_HEIGHT - 1];
    const gaps = bottomRow.filter(cell => cell === 0).length;
    expect(gaps).toBe(1);
  });

  test('pushes current piece up by 1', () => {
    const board = createEmptyBoard();
    const piece = { ...getPieceFromType('I'), y: 5 };
    const result = addGarbageRow(board, piece);
    expect(result.currentPiece.y).toBe(4);
  });

  test('handles null current piece', () => {
    const board = createEmptyBoard();
    const result = addGarbageRow(board, null);
    expect(result.currentPiece).toBe(null);
  });
});

describe('lockPieceToBoard', () => {
  test('locks piece to board', () => {
    const board = createEmptyBoard();
    const piece = { ...getPieceFromType('O'), x: 4, y: 5 };
    const newBoard = lockPieceToBoard(piece, board);

    // O piece is 2x2, so it should fill 4 cells
    expect(newBoard[5][4]).toBe(piece.color);
    expect(newBoard[5][5]).toBe(piece.color);
    expect(newBoard[6][4]).toBe(piece.color);
    expect(newBoard[6][5]).toBe(piece.color);
  });

  test('does not modify original board', () => {
    const board = createEmptyBoard();
    const piece = { ...getPieceFromType('O'), x: 4, y: 5 };
    lockPieceToBoard(piece, board);

    // Original board should still be empty
    expect(board[5][4]).toBe(0);
  });
});

describe('clearRows', () => {
  test('returns 0 rows cleared for empty board', () => {
    const board = createEmptyBoard();
    const result = clearRows(board);
    expect(result.rowsCleared).toBe(0);
  });

  test('clears one complete row', () => {
    const board = createEmptyBoard();
    board[10].fill('#ff0000'); // Fill row 10
    const result = clearRows(board);
    expect(result.rowsCleared).toBe(1);
  });

  test('clears multiple complete rows', () => {
    const board = createEmptyBoard();
    board[10].fill('#ff0000');
    board[11].fill('#00ff00');
    board[12].fill('#0000ff');
    const result = clearRows(board);
    expect(result.rowsCleared).toBe(3);
  });

  test('adds empty rows at top after clearing', () => {
    const board = createEmptyBoard();
    board[19].fill('#ff0000'); // Fill bottom row
    const result = clearRows(board);
    expect(result.board[0].every(cell => cell === 0)).toBe(true);
  });

  test('maintains board height after clearing', () => {
    const board = createEmptyBoard();
    board[18].fill('#ff0000');
    board[19].fill('#00ff00');
    const result = clearRows(board);
    expect(result.board.length).toBe(BOARD_HEIGHT);
  });
});

describe('generatePieceBag', () => {
  test('returns array of 7 pieces', () => {
    const bag = generatePieceBag();
    expect(bag.length).toBe(7);
  });

  test('contains all 7 tetromino types', () => {
    const bag = generatePieceBag();
    const types = new Set(bag);
    expect(types.size).toBe(7);
    expect(types.has('I')).toBe(true);
    expect(types.has('O')).toBe(true);
    expect(types.has('T')).toBe(true);
    expect(types.has('S')).toBe(true);
    expect(types.has('Z')).toBe(true);
    expect(types.has('J')).toBe(true);
    expect(types.has('L')).toBe(true);
  });
});

describe('createPieceQueue', () => {
  test('creates queue with correct length', () => {
    const queue = createPieceQueue(2);
    expect(queue.length).toBe(14); // 2 bags * 7 pieces
  });

  test('uses default bag count of 14', () => {
    const queue = createPieceQueue();
    expect(queue.length).toBe(98); // 14 bags * 7 pieces
  });
});