The Bowling Game Kata

bowling.go

//bowling.go
package bowling

type Game struct {
	rolls []int
	currentRoll int
}

func NewGame() *Game {
	return &Game{make([]int, 21), 0}
}

func (g *Game) Roll(p int) {
	g.rolls[g.currentRoll] = p
	g.currentRoll++
}

func (g *Game) Score() int {
	score := 0
	frame := 0
	for i := 0; i < 10; i++ {
		if g.isStrike(frame) {
			score += 10 + g.strikeBonus(frame)
			frame++
		} else if g.isSpare(frame) {
			score += 10 + g.spareBonus(frame)
			frame += 2
		} else {
			score += g.sumOfRolls(frame)
			frame += 2
		}
	}
	return score
}

func (g *Game) isStrike(frame int) bool {
	return g.rolls[frame] == 10
}

func (g *Game) isSpare(frame int) bool {
	return g.sumOfRolls(frame) == 10
}

func (g *Game) strikeBonus(frame int) int {
	return g.rolls[frame+1] + g.rolls[frame+2]
}

func (g *Game) spareBonus(frame int) int {
	return g.rolls[frame+2]
}

func (g *Game) sumOfRolls(frame int) int {
	return g.rolls[frame] + g.rolls[frame+1]
}

//bowling_test.go
package bowling

import (
	"testing"
	"fmt"
)

func rollMany(n, pins int, g *Game) {
	for i := 0; i < n; i++ {
		g.Roll(pins)
	}
}

func assertScore(n int, g *Game, t *testing.T) {
	score := g.Score()
	if score != n {
		t.Fail()
		fmt.Printf("Expected score %d and got %d", n, score)
	}
}

func TestZero(t *testing.T) {
	g := NewGame()
	rollMany(20, 0, g)
	assertScore(0, g, t)
}

func TestAllOnes(t *testing.T) {
	g := NewGame()
	rollMany(20, 1, g)
	assertScore(20, g, t)
}

func TestOneSpare(t *testing.T) {
	g := NewGame()
	g.Roll(5)
	g.Roll(5) // spare
	g.Roll(3)
	rollMany(17, 0, g)
	assertScore(16, g, t)
}

func TestOneStrike(t *testing.T) {
	g := NewGame()
	g.Roll(10) //strike
	g.Roll(3)
	g.Roll(4)
	rollMany(16, 0, g)
	assertScore(24, g, t)
}

func TestPerfectGame(t *testing.T) {
	g := NewGame()
	rollMany(12, 10, g)
	assertScore(300, g, t)
}