BowlingKata.rb

class BowlingGame
  attr_accessor :scorecard
  def score
    @scorecard.size.times.map { |i| frame_score(@scorecard[i, 3]) }.reduce(:+)
  end

  def frame_score(frames)
    if strike_or_spare?(frames.first)
      frames.flatten.first(3).reduce(:+)
    else
      frames.first.reduce(:+)
    end
  end

  def strike_or_spare?(frame)
    frame.reduce(:+) == 10 
  end
end

describe BowlingGame do
  let(:game) {BowlingGame.new}

  context "#score" do
    it "is 0 for game with all gutters" do
      game.scorecard = [[0, 0]] * 10
      expect(game.score).to eq 0
    end

    it "is 20 for game with all ones" do
      game.scorecard = [[1, 1]] * 10
      expect(game.score).to eq 20
    end

    it "is 16 for game with spare followed by 3" do
      game.scorecard = [[3, 7], [3, 0]] + [[0,0]] * 8
      expect(game.score).to eq 16
    end

    it "is 24 for game with strike followed by 3 and 4" do
      game.scorecard = [[10], [3,4]] + [[0,0]] * 8
      expect(game.score).to eq 24
    end

    it "is 300 for perfect game" do
      game.scorecard = [[10]] * 9 + [[10, 10, 10]]
      expect(game.score).to eq 300
    end

    it "handles one strike" do
      game.scorecard = [[10]]
      expect(game.score).to eq 10
    end

    it "handles two strikes" do
      game.scorecard = [[10], [10]]
      expect(game.score).to eq 30
    end

    it "handles a random smattering" do
      game.scorecard = [[10], [10], [3, 7], [4, 5], [3, 5], [4]]
      expect(game.score).to eq 78
    end
  end
end