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to Bowling in the Ruby Track

Published at Jun 05 2020 · 0 comments
Instructions
Test suite
Solution

Score a bowling game.

Bowling is a game where players roll a heavy ball to knock down pins arranged in a triangle. Write code to keep track of the score of a game of bowling.

Scoring Bowling

The game consists of 10 frames. A frame is composed of one or two ball throws with 10 pins standing at frame initialization. There are three cases for the tabulation of a frame.

  • An open frame is where a score of less than 10 is recorded for the frame. In this case the score for the frame is the number of pins knocked down.

  • A spare is where all ten pins are knocked down by the second throw. The total value of a spare is 10 plus the number of pins knocked down in their next throw.

  • A strike is where all ten pins are knocked down by the first throw. The total value of a strike is 10 plus the number of pins knocked down in the next two throws. If a strike is immediately followed by a second strike, then the value of the first strike cannot be determined until the ball is thrown one more time.

Here is a three frame example:

Frame 1 Frame 2 Frame 3
X (strike) 5/ (spare) 9 0 (open frame)

Frame 1 is (10 + 5 + 5) = 20

Frame 2 is (5 + 5 + 9) = 19

Frame 3 is (9 + 0) = 9

This means the current running total is 48.

The tenth frame in the game is a special case. If someone throws a strike or a spare then they get a fill ball. Fill balls exist to calculate the total of the 10th frame. Scoring a strike or spare on the fill ball does not give the player more fill balls. The total value of the 10th frame is the total number of pins knocked down.

For a tenth frame of X1/ (strike and a spare), the total value is 20.

For a tenth frame of XXX (three strikes), the total value is 30.

Requirements

Write code to keep track of the score of a game of bowling. It should support two operations:

  • roll(pins : int) is called each time the player rolls a ball. The argument is the number of pins knocked down.
  • score() : int is called only at the very end of the game. It returns the total score for that game.

For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby bowling_test.rb

To include color from the command line:

ruby -r minitest/pride bowling_test.rb

Source

The Bowling Game Kata at but UncleBob http://butunclebob.com/ArticleS.UncleBob.TheBowlingGameKata

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

bowling_test.rb

require 'minitest/autorun'
require_relative 'bowling'

# Common test data version: 1.2.0 1806718
class BowlingTest < Minitest::Test
  def test_should_be_able_to_score_a_game_with_all_zeros
    # skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 0, game.score
  end

  def test_should_be_able_to_score_a_game_with_no_strikes_or_spares
    skip
    game = Game.new
    rolls = [3, 6, 3, 6, 3, 6, 3, 6, 3, 6, 3, 6, 3, 6, 3, 6, 3, 6, 3, 6]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 90, game.score
  end

  def test_a_spare_followed_by_zeros_is_worth_ten_points
    skip
    game = Game.new
    rolls = [6, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 10, game.score
  end

  def test_points_scored_in_the_roll_after_a_spare_are_counted_twice
    skip
    game = Game.new
    rolls = [6, 4, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 16, game.score
  end

  def test_consecutive_spares_each_get_a_one_roll_bonus
    skip
    game = Game.new
    rolls = [5, 5, 3, 7, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 31, game.score
  end

  def test_a_spare_in_the_last_frame_gets_a_one_roll_bonus_that_is_counted_once
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 3, 7]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 17, game.score
  end

  def test_a_strike_earns_ten_points_in_a_frame_with_a_single_roll
    skip
    game = Game.new
    rolls = [10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 10, game.score
  end

  def test_points_scored_in_the_two_rolls_after_a_strike_are_counted_twice_as_a_bonus
    skip
    game = Game.new
    rolls = [10, 5, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 26, game.score
  end

  def test_consecutive_strikes_each_get_the_two_roll_bonus
    skip
    game = Game.new
    rolls = [10, 10, 10, 5, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 81, game.score
  end

  def test_a_strike_in_the_last_frame_gets_a_two_roll_bonus_that_is_counted_once
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 7, 1]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 18, game.score
  end

  def test_rolling_a_spare_with_the_two_roll_bonus_does_not_get_a_bonus_roll
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 7, 3]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 20, game.score
  end

  def test_strikes_with_the_two_roll_bonus_do_not_get_bonus_rolls
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 30, game.score
  end

  def test_a_strike_with_the_one_roll_bonus_after_a_spare_in_the_last_frame_does_not_get_a_bonus
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 3, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 20, game.score
  end

  def test_all_strikes_is_a_perfect_game
    skip
    game = Game.new
    rolls = [10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 300, game.score
  end

  def test_rolls_cannot_score_negative_points
    skip
    game = Game.new
    rolls = []
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(-1)
    end
  end

  def test_a_roll_cannot_score_more_than_10_points
    skip
    game = Game.new
    rolls = []
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(11)
    end
  end

  def test_two_rolls_in_a_frame_cannot_score_more_than_10_points
    skip
    game = Game.new
    rolls = [5]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(6)
    end
  end

  def test_bonus_roll_after_a_strike_in_the_last_frame_cannot_score_more_than_10_points
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(11)
    end
  end

  def test_two_bonus_rolls_after_a_strike_in_the_last_frame_cannot_score_more_than_10_points
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 5]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(6)
    end
  end

  def test_two_bonus_rolls_after_a_strike_in_the_last_frame_can_score_more_than_10_points_if_one_is_a_strike
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10, 6]
    rolls.each { |pins| game.roll(pins) }
    assert_equal 26, game.score
  end

  def test_the_second_bonus_rolls_after_a_strike_in_the_last_frame_cannot_be_a_strike_if_the_first_one_is_not_a_strike
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 6]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(10)
    end
  end

  def test_second_bonus_roll_after_a_strike_in_the_last_frame_cannot_score_more_than_10_points
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(11)
    end
  end

  def test_an_unstarted_game_cannot_be_scored
    skip
    game = Game.new
    rolls = []
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.score
    end
  end

  def test_an_incomplete_game_cannot_be_scored
    skip
    game = Game.new
    rolls = [0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.score
    end
  end

  def test_cannot_roll_if_game_already_has_ten_frames
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(0)
    end
  end

  def test_bonus_rolls_for_a_strike_in_the_last_frame_must_be_rolled_before_score_can_be_calculated
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.score
    end
  end

  def test_both_bonus_rolls_for_a_strike_in_the_last_frame_must_be_rolled_before_score_can_be_calculated
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.score
    end
  end

  def test_bonus_roll_for_a_spare_in_the_last_frame_must_be_rolled_before_score_can_be_calculated
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 3]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.score
    end
  end

  def test_cannot_roll_after_bonus_roll_for_spare
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 3, 2]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(2)
    end
  end

  def test_cannot_roll_after_bonus_rolls_for_strike
    skip
    game = Game.new
    rolls = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 3, 2]
    rolls.each { |pins| game.roll(pins) }
    assert_raises Game::BowlingError do
      game.roll(2)
    end
  end
end
# frozen_string_literal: true

# Write your code for the 'Bowling' exercise in this file. Make the tests in
# `bowling_test.rb` pass.
#
# To get started with TDD, see the `README.md` file in your
# `ruby/bowling` directory.

class Game
  def initialize
    @frames = Array.new(11) { Frame.new }
    @current_frame = 0
  end

  def roll(pins)
    validate_game_unfinished
    validate_pins_in_range(pins)

    @current_frame += 1 if @frames[@current_frame].start_next_frame?

    @frames[0..@current_frame].each { |frame| frame << pins }
  end

  def score
    validate_game_finished

    @frames[0..9].map(&:score).inject(:+)
  end

  private

  def last_frame
    @frames[9]
  end

  def validate_game_unfinished
    raise BowlingError unless last_frame.extendable?
  end

  def validate_game_finished
    raise BowlingError if last_frame.extendable?
  end

  def validate_pins_in_range(pins)
    raise BowlingError unless (0..10).include?(pins)
  end

  class Frame
    def initialize
      @rolls = []
    end

    def <<(score)
      @rolls << score if extendable?

      validate_frame
    end

    def extendable?
      @rolls.length < 2 || (strike? && fill_ball?) || (spare? && fill_ball?)
    end

    def start_next_frame?
      strike? || full?
    end

    def score
      @rolls.inject(:+)
    end

    private

    def first_roll
      @rolls[0]
    end

    def second_roll
      @rolls[1]
    end

    def full?
      @rolls.length == 2
    end

    def strike?
      first_roll == 10
    end

    def spare?
      first_roll + second_roll == 10
    end

    def fill_ball?
      @rolls.length < 3
    end

    def validate_frame
      raise BowlingError if !strike? && full? && first_roll + second_roll > 10
    end
  end

  class BowlingError < StandardError; end
end

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