@Test
public void testDiagonalWinnerReturnsOneForSecondDiagonal() {
int[] cell1 = {1, 1};
int[] cell2 = {0, 0};
board.setCellValue(cell1, 1);
board.setCellValue(cell2, 0);
assertEquals(1, GameState.DiagonalWinner(board));
}
@Test
public void testDiagonalWinnerReturnsZeroForNoWinner() {
assertEquals(0, GameState.DiagonalWinner(board));
}