GildedRose kata

gilded_rose.rb

ITEM_AGED_BRIE = "Aged Brie".freeze
ITEM_BACKSTAGE_PASS = "Backstage passes to a TAFKAL80ETC concert".freeze
ITEM_SULFURAS = "Sulfuras, Hand of Ragnaros".freeze

class GildedRose
  def initialize(items)
    @items = items
  end

  def update_quality()
    @items.each(&:update!)
  end
end

class Item
  class << self
    def new(name, sell_in, quality)
      if self == Item
        case name
        when ITEM_AGED_BRIE then AgedBrie.new(name, sell_in, quality)
        when ITEM_BACKSTAGE_PASS then BackstagePass.new(name, sell_in, quality)
        when ITEM_SULFURAS then Sulfuras.new(name, sell_in, quality)
        else BasicItem.new(name, sell_in, quality)
        end
      else
        super
      end
    end
  end

  def initialize(name, sell_in, quality)
    @name = name
    @sell_in = sell_in
    @quality = quality
  end

  def to_s()
    "#{@name}, #{@sell_in}, #{@quality}"
  end

  def name
    @name
  end

  def sell_in
    @sell_in
  end

  def quality
    @quality
  end

  def update!
    update_sell_in!
    update_quality!
    clamp_quality!
  end

  def update_sell_in!
    @sell_in = @sell_in - 1
  end

  def update_quality!
    raise "Override in subclass"
  end

  def clamp_quality!
    @quality = [@quality, 0].max
    @quality = [@quality, 50].min
  end
end

class BasicItem < Item
  def update_quality!
    if @sell_in < 0
      @quality -= 2
    else
      @quality -= 1
    end
  end
end

class AgedBrie < Item
  def update_quality!
    if @sell_in < 0
      @quality += 2
    else
      @quality += 1
    end
  end
end

class BackstagePass < Item
  def update_quality!
    case @sell_in
    when 11..Float::INFINITY then @quality += 1
    when 5..10 then @quality += 2
    when 0..5 then @quality += 3
    else @quality = 0
    end
  end
end

class Sulfuras < Item
  def update_sell_in!; end

  def update_quality!; end

  def clamp_quality!; end
end

gilded_rose_spec.rb

require File.join(File.dirname(__FILE__), 'gilded_rose')

shared_examples "ends with sell_in" do |new_sell_in|
  it do
    GildedRose.new(items).update_quality() 
    expect(items[0].sell_in).to eq(new_sell_in)
  end
end

shared_examples "ends with quality" do |new_quality|
  it do
    GildedRose.new(items).update_quality() 
    expect(items[0].quality).to eq(new_quality)
  end
end

describe GildedRose do
  describe "#update_quality" do
    let(:item_name) { "foo" }
    let(:items) { [Item.new(item_name, sell_in, quality)] }

    it "does not change the name" do
      items = [Item.new(item_name, 0, 0)]
      GildedRose.new(items).update_quality()
      expect(items[0].name).to eq("foo")
    end

    context "when the sell by date has not passed" do
      let(:sell_in) { 1 }

      context "for basic item" do
        context "when quality is 0" do
          let(:quality) { 0 }

          it_behaves_like "ends with sell_in", 0

          it_behaves_like "ends with quality", 0
        end

        context "when quality is greater than 0" do
          let(:quality) { 10 }

          it_behaves_like "ends with sell_in", 0

          it_behaves_like "ends with quality", 9
        end
      end

      context "for Aged Brie" do
        let(:item_name) { "Aged Brie" }

        context "when quality is 50" do
          let(:quality) { 50 }

          it_behaves_like "ends with sell_in", 0

          it_behaves_like "ends with quality", 50
        end

        context "when quality is less than 50" do
          let(:quality) { 10 }

          it_behaves_like "ends with sell_in", 0

          it_behaves_like "ends with quality", 11
        end
      end

      context "for Sulfuras" do
        let(:item_name) { "Sulfuras, Hand of Ragnaros" }
        let(:quality) { 80 }

        it_behaves_like "ends with sell_in", 1

        it_behaves_like "ends with quality", 80
      end

      context "for Backstage" do
        let(:item_name) { "Backstage passes to a TAFKAL80ETC concert" }
        let(:quality) { 10 }

        context "when sell_in is more than 10" do
          let(:sell_in) { 15 }

          it_behaves_like "ends with sell_in", 14

          it_behaves_like "ends with quality", 11
        end

        context "when sell_in is >5 but <=10" do
          let(:sell_in) { 10 }

          it_behaves_like "ends with sell_in", 9

          it_behaves_like "ends with quality", 12
        end

        context "when sell_in is <=5" do
          let(:sell_in) { 5 }

          it_behaves_like "ends with sell_in", 4

          it_behaves_like "ends with quality", 13
        end
      end
    end

    context "when the sell by date has passed" do
      let(:sell_in) { -1 }

      context "for basic item" do
        context "when quality is 0" do
          let(:quality) { 0 }

          it_behaves_like "ends with sell_in", -2

          it_behaves_like "ends with quality", 0
        end

        context "when quality is greater than 0" do
          let(:quality) { 10 }

          it_behaves_like "ends with sell_in", -2

          it_behaves_like "ends with quality", 8
        end
      end

      context "for Aged Brie" do
        let(:item_name) { "Aged Brie" }

        context "when quality is 50" do
          let(:quality) { 50 }

          it_behaves_like "ends with sell_in", -2

          it_behaves_like "ends with quality", 50
        end

        context "when quality is less than 50" do
          let(:quality) { 10 }

          it_behaves_like "ends with sell_in", -2

          it_behaves_like "ends with quality", 12
        end
      end

      context "for Sulfuras" do
        let(:item_name) { "Sulfuras, Hand of Ragnaros" }
        let(:quality) { 80 }

        it_behaves_like "ends with sell_in", -1

        it_behaves_like "ends with quality", 80
      end

      context "for Backstage" do
        let(:item_name) { "Backstage passes to a TAFKAL80ETC concert" }
        let(:quality) { 10 }

        it_behaves_like "ends with sell_in", -2

        it_behaves_like "ends with quality", 0
      end
    end
  end
end