@Test
void strike() {
  var game = new Game();
  var firstRollPins = 10;
  var secondRollPins = 5;
  var thirdRollPins = 3;
  game.roll(firstRollPins);
  game.roll(secondRollPins);
  game.roll(thirdRollPins);
  
  var score = game.score();

  assertThat(score
    .isEqualTo(
      firstRollPins +
      (secondRollPins + thirdRollPins) * 2);
}

public int score() {
  int score = firstRoll + secondRoll;
  if (previous != null) {
    if (previous.strike) {
      score *= 2;
    } else if (previous.spare) {
      score += firstRoll;
    }
  }
  return score;
}