first test and first implementation

gistfile1.xtend

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

// the implementation so far...
class Game {
  
	def roll(int score) {
	}
	
	def score() {
		0
	}
}