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# tmszrbn's solution

## to Bowling in the Ruby Track

Published at Feb 15 2020 · 1 comment
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``````
``````require 'forwardable'

class Game
class BowlingError < StandardError; end
extend Forwardable
def initialize
@score = 0
@frames = Frames.new
@roll_factor = 1
@next_roll_factor = 1
end

def roll(pins)
raise BowlingError if completed? || pins < 0
@score += evaluate_score(pins)
@frames << pins
bonuses
end

def score
raise BowlingError unless completed? && started?
@score
end

private

def_delegators :@frames, :started?, :completed?, :roll_bonus?, :next_roll_bonus?

def bonuses
@roll_factor, @next_roll_factor = @next_roll_factor, 1
@roll_factor += 1 if roll_bonus?
@next_roll_factor += 1 if next_roll_bonus?
end

def evaluate_score(pins)
result = pins * @roll_factor
result
end

class Frames
include Enumerable
extend Forwardable

def initialize
@array = ([LastFrame.new] + Array.new(9) { Frame.new })
@started = false
end

attr_reader :array
def_delegators :@array, :each, :size

def current
@current = @current.nil? || @current.end? ? @array&.pop : @current
end

def next_roll_bonus?
@current&.next_roll_bonus?
end

def roll_bonus?
@current&.roll_bonus?
end

def <<(pins)
current << pins  unless current.nil?
end

def completed?
return true if current.nil?
size == 0 && current.end?
end

def started?
@array.size < 10
end
end
class Frame
def initialize
@rolls = []
@spare = false
@strike = false
end

def end?
return true if @strike
@rolls.size >= 2
end

def <<(roll)
@rolls << roll
@strike = true if roll == 10
@spare = true if @rolls.sum == 10 && !strike?
raise BowlingError if @rolls.sum > 10
end

def roll_bonus?
(spare? || strike?) && !last?
end

def next_roll_bonus?
strike? && !last?
end

def spare?
@spare
end

def strike?
@strike
end

def last?
false
end

def spare_bonus!; end
end

class LastFrame < Frame
def initialize
@bonus_rolls = 0
@strikes = 0
super
end

def <<(roll)
raise BowlingError if roll == 10 && strike? && @rolls.size == 2 && @rolls.sum != 20
@strike = true if @rolls.size.zero? && roll == 10
@spare = true if @rolls.sum == 10 && !strike?
@rolls << roll
@strikes += 1 if roll == 10
raise BowlingError if roll > 10
raise BowlingError if @rolls.sum > 20 && @strikes < 2
@spare = true if @rolls.sum == 10
spare_bonus! if spare?
end

def end?
@rolls.size >= 2 + @bonus_rolls
end

def spare_bonus!
@bonus_rolls = 1
end

def strike_bonus!
@bonus_rolls = 1
end

def last?
true
end
end
end``````

## Community comments

Find this solution interesting? Ask the author a question to learn more.
Solution Author
commented 180 days ago

I wanted to do it with evaluation after each roll. Felt a little harder and more interesting.

(edited 180 days ago)

### What can you learn from this solution?

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