Bowling Game Kata

Game.java

package Bowling;


public class Game {
  int nrolls  = 0;
  int[] rolls = new int[21];

  public void roll(int pins) {
    rolls[nrolls++] = pins;
  }

  private boolean isStrike(int frameIdx) {
    return 10 == rolls[frameIdx];
  }

  private boolean isSpare(int frameIdx) {
    return 10 == rolls[frameIdx] + rolls[frameIdx + 1];
  }

  public int score() {
    int score    = 0;
    int frameIdx = 0;
    for (int frameNum = 0; frameNum < 10; ++frameNum) {
      if (isStrike(frameIdx)) {
        score    += 10 + rolls[frameIdx + 1] + rolls[frameIdx + 2];
        frameIdx += 1;
      } else if (isSpare(frameIdx)) {
        score    += 10 + rolls[frameIdx + 2];
        frameIdx += 2;
      } else {
        score    += rolls[frameIdx] + rolls[frameIdx + 1];
        frameIdx += 2;
      }
    } return score;
  }
}

GameTest.java

import Bowling.Game;
import junit.framework.TestCase;


public class GameTest extends TestCase {
  Game g;

  protected void setUp() {
    g = new Game();
  }

  protected void tearDown() {
    g = null;
  }

  private void rollMany(int n, int pins) {
    for (int roll = 0; roll < n; ++roll)
      g.roll(pins);
  }

  private void rollSpare() {
    rollMany(2, 5);
  }

  private void rollStrike() {
    g.roll(10);
  }

  public void testGutterGame() {
    rollMany(20, 0);
    assertEquals(0, g.score());
  }

  public void testAllOnes() {
    rollMany(20, 1);
    assertEquals(20, g.score());
  }

  public void testOneSpare() {
    rollSpare();
    g.roll(3);
    rollMany(17, 0);
    assertEquals(16, g.score());
  }

  public void testOneStrike() {
    rollStrike();
    g.roll(5);
    g.roll(4);
    rollMany(16, 0);
    assertEquals(28, g.score());
  }

  public void testPerfectGame() {
    rollMany(12, 10);
    assertEquals(300, g.score());
  }
}