Bowling Kata

Game.java

public class Game {
	private static final int MAX_ROLLS_IN_GAME = 21;
	private static final int FRAMES_IN_GAME = 10;
	
	private int rolls[] = new int [MAX_ROLLS_IN_GAME];
	private int currRoll;
	
	public void roll(int pins) {
		rolls[currRoll] = pins;
		currRoll++;
	}

	public int score() {
		int score = 0;
		int frameIndex = 0;
		for (int i = 0; i < FRAMES_IN_GAME; i++) {
			if (isStrike(frameIndex)) {
				score += strikeFrameScore(frameIndex) + strikeBonus(frameIndex);
				frameIndex++;
			} else if (isSpare(frameIndex)) {
				score += fullFrameScore(frameIndex) + spareBonus(frameIndex);
				frameIndex += 2;
			} else {
				score += fullFrameScore(frameIndex);
				frameIndex += 2;
			}
		}
		return score;
	}

	private int strikeBonus(int frameIndex) {
		return rolls[frameIndex + 1] + rolls[frameIndex + 2];
	}

	private int strikeFrameScore(int frameIndex) {
		return rolls[frameIndex];
	}

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

	private int spareBonus(int frameIndex) {
		return rolls[frameIndex + 2];
	}

	private int fullFrameScore(int frameIndex) {
		return rolls[frameIndex] + rolls[frameIndex + 1];
	}

	private boolean isSpare(int frameIndex) {
		return fullFrameScore(frameIndex) == 10;
	}
}

GameTest.java

import static org.junit.Assert.*;

import org.junit.Before;
import org.junit.Test;



public class GameTest {
	private Game g;

	@Before
	public void setUp() {
		g = new Game();
	}
	
	@Test
	public void gutterGameScoreIsZero() throws Exception {
		rollMany(0, 20);
		
		assertEquals(0, g.score());
	}
	
	@Test
	public void gameWithOnlyOnesScoreIs20() throws Exception {
		rollMany(1, 20);
		
		assertEquals(20, g.score());
	}

	private void rollMany(int pins, int n) {
		for (int i = 0; i < n; i++) {
			g.roll(pins);
		}
	}
	
	@Test
	public void oneSpareShouldGetBonusForThatSpare() throws Exception {
		rollSpare();
		g.roll(3);
		
		rollMany(0, 17);
		
		assertEquals(10 + 3 + 3, g.score());
	}

	private void rollSpare() {
		g.roll(5);
		g.roll(5);
	}
	
	@Test
	public void oneStrikeShouldGetBonusForThatStrike() throws Exception {
		rollStrike();
		g.roll(3);
		g.roll(4);
		
		rollMany(0, 16);
		
		assertEquals(10 + 3 + 4 + 3 + 4, g.score());
	}

	private void rollStrike() {
		g.roll(10);
	}
	
	@Test
	public void perfectGame() throws Exception {
		rollMany(10, 12);
		
		assertEquals(300, g.score());
	}
}