bowling game test and implementation

gistfile1.java

package de.sprengerjo.game.xtend

import static org.junit.Assert.*
import org.junit.Test
import org.junit.Before

class GameTest {
  var game = new Game()

	@Before
	def void setUp() {
		game = new Game()
	}

	@Test
	def void gutterGamesOnly() {
		(1 .. 20).forEach[game.roll(0)]
		assertEquals(20 * 0, game.score())
	}

	@Test
	def void oneGamesOnly() {
		(1 .. 20).forEach[game.roll(1)]
		assertEquals(20 * 1, game.score())
	}

	@Test
	def void oneSpareAnd18OneGames() {
		rollSpare()
		(3 .. 20).forEach[game.roll(1)]
		assertEquals(5 + 5 + 1 + 18 * 1, game.score())
	}

	def rollSpare() {
		game.roll(5)
		game.roll(5)
	}

	@Test
	def void oneStrikeAnd18OneGames() {
		game.roll(10)
		(3 .. 20).forEach[game.roll(1)]
		assertEquals(10 + 1 + 1 + 18 * 1, game.score())
	}

	@Test
	def void perfectGameScoreIs300() {
		(1 .. 12).forEach[game.roll(10)]
		assertEquals(300, game.score())
	}
}

// game impl...
package de.sprengerjo.game.xtend

class Game {

  @Property // sugar for producing getter and setter in Java file
	var scores = newArrayList(0)

	def roll(int i) {
		scores.add(i)
	}

	def score() {
		var score = 0
		var roll = 1
		for (i : 0 ..< 10) {
			if (isStrike(roll)) {
				score = score + strikeBonus(roll)
				roll = roll + 1
			} else if (isSpare(roll)) {
				score = score + 10 + scores.get(roll + 2)
				roll = roll + 2
			} else {
				score = score + scores.get(roll) + scores.get(roll + 1)
				roll = roll + 2
			}
		}
		score
	}

	def isSpare(int roll) {
		10 == scores.get(roll) + scores.get(roll + 1)
	}

	def isStrike(int roll) {
		10 == scores.get(roll)
	}

	def strikeBonus(int roll) {
		10 + scores.get(roll + 1) + scores.get(roll + 2)
	}
}