Test-Driven Java Development - Second Edition

Test – O plays right after X

Now, we should make sure that players are changing. After X is finished, it should be O's turn, then again X, and so on:

@Testpublic void givenLastTurnWasXWhenNextPlayerThenO() {
  ticTacToe.play(1, 1);
  assertEquals('O', ticTacToe.nextPlayer());
}

If the last turn was played by X, then the next turn should be played by O.