exercism.io BeerSong

beer_song.rb

class BeerSong
  attr_reader :number

  def verse(number)
    @number = number
    take_it_away_guys!
  end

  def verses(first, last)
    first.downto(last).map { |x| verse x }.join("\n") << "\n"
  end

  def sing
    verses(99, 0)
  end

  private

  def take_it_away_guys!
    "#{number_of_bottles.capitalize} of beer on the wall, " \
    "#{number_of_bottles} of beer.\n" \
    "#{take_whatever_down or go_to_the_store}, " \
    "#{one_fewer_bottles} of beer on the wall.\n"
  end

  def number_of_bottles(override=nil)
    case override or number
      when 0 then "no more bottles"
      when 1 then "1 bottle"
      else "#{override or number} bottles"
    end
  end

  def take_whatever_down
    "Take #{number == 1 ? "it" : "one"} down and pass it around" unless number.zero?
  end

  def go_to_the_store
    "Go to the store and buy some more" # but don't drive
  end

  def one_fewer_bottles
    number_of_bottles (number - 1) % 100 # thanks @thomvil :)
  end
end

beer_song_test.rb

require 'minitest/autorun'
require_relative 'beer_song'

class BeerSongTest < MiniTest::Unit::TestCase
  def song
    @song = ::BeerSong.new
  end

  def teardown
    @song = nil
  end

  def test_a_typical_verse
    expected = "8 bottles of beer on the wall, 8 bottles of beer.\n" \
      "Take one down and pass it around, 7 bottles of beer on the wall.\n"
    assert_equal expected, song.verse(8)
  end

  def test_another_typical_verse
    skip
    expected = "3 bottles of beer on the wall, 3 bottles of beer.\n" \
      "Take one down and pass it around, 2 bottles of beer on the wall.\n"
    assert_equal expected, song.verse(3)
  end

  def test_verse_1
    skip
    expected = "1 bottle of beer on the wall, 1 bottle of beer.\n" \
      "Take it down and pass it around, no more bottles of beer on the wall.\n"
    assert_equal expected, song.verse(1)
  end

  def test_verse_2
    skip
    expected = "2 bottles of beer on the wall, 2 bottles of beer.\n" \
      "Take one down and pass it around, 1 bottle of beer on the wall.\n"
    assert_equal expected, song.verse(2)
  end

  def test_verse_0
    skip
    expected =
      "No more bottles of beer on the wall, no more bottles of beer.\n" \
      "Go to the store and buy some more, 99 bottles of beer on the wall.\n"
    assert_equal expected, song.verse(0)
  end

  def test_several_verses
    skip
    expected = "8 bottles of beer on the wall, 8 bottles of beer.\n" \
      "Take one down and pass it around, 7 bottles of beer on the wall.\n\n" \
      "7 bottles of beer on the wall, 7 bottles of beer.\n" \
      "Take one down and pass it around, 6 bottles of beer on the wall.\n\n" \
      "6 bottles of beer on the wall, 6 bottles of beer.\n" \
      "Take one down and pass it around, 5 bottles of beer on the wall.\n\n"
    assert_equal expected, song.verses(8, 6)
  end

  def test_the_whole_song
    skip
    assert_equal song.verses(99, 0), song.sing
  end
end