As with almost everything else done in the TDD fashion, implementation is fairly easy:
private int turn = 0; ... public String play(int x, int y) { checkAxis(x); checkAxis(y); lastPlayer = nextPlayer(); setBox(new TicTacToeBean(++turn, x, y, lastPlayer)); if (isWin(x, y)) { return lastPlayer + " is the winner"; } else if (isDraw()) { return RESULT_DRAW; } else { return NO_WINNER; } }