TDDBC TOKYO 1.5 VendingMachine

vending_machine.rb

# -*- coding: utf-8 -*-
class Drink
  attr_accessor :name, :price
  def initialize(name, price)
    self.name = name
    self.price = price
  end
end

class Money
  attr_reader :value
end

[10, 50, 100, 500, 1000].each do |v|
  klass = Class.new(Money) do
    define_method :initialize do
      @value = v
    end

    define_method :to_s do
      "Money" + v.to_s
    end
  end
  Kernel.const_set "Money#{v}", klass.new
end

class VendingMachine
  attr_reader :amount, :sales, :charges
  def initialize
    @sales = 0
    @amount = 0
    cola = Drink.new "コーラ", 120
    redbull = Drink.new "レッドブル", 200
    water = Drink.new "水", 100

    @drink = {1 => cola, 2 => redbull, 3 => water}
    @stock = {1 => 5, 2 => 5, 3 => 5}
    @charges = {
        Money10   => 10,
        Money50   => 10,
        Money100  => 10,
        Money500  => 10,
        Money1000 =>  5,
    }
  end

  def count_stock(id)
    @stock[id] || 0
  end

  def receive(money)
    if money.is_a? Money
      @amount += money.value
    else
      raise "変なもんいれんな"
    end
    ret = []
    @charges[money] += 1
    @drink.each do |id,drink|
      if @amount >= drink.price
        ret.push id
      end
    end
    ret
  end

  def sell(id)
    if @amount < @drink[id].price
      raise "買えません"
    end
    if count_stock(id) <= 0
      raise "売り切れです"
    end

    oturi = @amount - @drink[id].price
    needed = {}
    [1000,500,100,50,10].each do |m|
      needed[Kernel.const_get "Money#{m}"] = oturi / m
      oturi %= m
    end

    if needed.any? {|k,v| v > @charges[k]}
      raise "お釣りがありません"
    end
    needed.each do |k,v|
      @charges[k] -= v
    end

    @sales += @drink[id].price
    @stock[id] -= 1
    @amount = 0
  end
end

vending_machine_spec.rb

# -*- coding: utf-8 -*-
$LOAD_PATH.unshift File.dirname(__FILE__)
require 'vending_machine'

describe VendingMachine do
  def buy_cola(just = nil)
    if just
      @vm.receive(Money100)
      @vm.receive(Money10)
      @vm.receive(Money10)
    else
      @vm.receive(Money500)
    end
    @vm.sell(1)
  end

  before do
    @vm = VendingMachine.new
  end
  describe '#receive' do
    context '千円札を投入すると' do
      it '合計金額が千円' do
        @vm.receive(Money1000)
        @vm.amount.should == 1000
      end
      it 'コーラ, レッドブル, 水が買えることを示す' do
        @vm.receive(Money1000).should == [1, 2, 3]
      end
    end
    [Money10, Money50, Money100, Money500].each do |coin|
      context "#{coin.value}円玉を投入すると" do
        it "合計金額が#{coin.value}円" do
          @vm.receive(coin)
          @vm.amount.should == coin.value
        end
      end
    end
    context '二千円札を投入すると' do
      it 'RuntimeError が発生する' do
        expect{@vm.receive('二千円札')}.to raise_error(RuntimeError, "変なもんいれんな")
      end
    end
    context '千円札と100円玉を投入すると' do
      it '合計金額が1100円' do
        @vm.receive(Money1000)
        @vm.receive(Money100)
        @vm.amount.should == 1100
      end
    end
    context '100円玉を投入すると' do
      it '水しか買えないことを示す' do
        @vm.receive(Money100).should == [3]
      end
    end
    context '120円を投入すると' do
      it '水とコーラが買えることを示す' do
        @vm.receive(Money100).should == [3]
        @vm.receive(Money10).should == [3]
        @vm.receive(Money10).should == [1,3]
      end
    end
  end
  describe '#count_stock' do
    it 'コーラの在庫を返す' do
      @vm.count_stock(1).should == 5
    end
    it 'レッドブルの在庫を返す' do
      @vm.count_stock(2).should == 5
    end
    it '水の在庫を返す' do
      @vm.count_stock(3).should == 5
    end
  end

  describe '#sell' do
    context 'id=1 を指定すると' do
      before do
        buy_cola
      end
      it 'コーラの在庫が減る' do
        @vm.count_stock(1).should == 4
      end
      it 'おつりが返るので残金は0' do
        @vm.amount.should == 0
      end
    end

    context "id=2 を指定すると" do
      it "レッドブルの在庫が減る" do
        @vm.receive(Money500)
        @vm.sell(2)
        @vm.count_stock(2).should == 4
      end
    end

    context '金額が足りない場合' do
      it 'RuntimeError が発生する' do
        @vm.receive(Money50)
        expect{@vm.sell(1)}.to raise_error(RuntimeError, "買えません")
      end
    end
    context "コーラの在庫がない場合" do
      before do
        5.times{ buy_cola(true) }
      end
      it "RuntimeError が発生する" do
        expect{buy_cola}.to raise_error(RuntimeError, "売り切れです")
      end
    end
  end

  describe "#sales" do
    context 'コーラを二本買った場合' do
      before do
        2.times { buy_cola }
      end
      it '売り上げ合計金額を返す' do
        @vm.sales.should == 240
      end
    end
  end

  describe "#charges" do
    it "千円札5枚、硬貨はそれぞれ10枚保持している" do
      @vm.charges.should == {
        Money10   => 10,
        Money50   => 10,
        Money100  => 10,
        Money500  => 10,
        Money1000 =>  5,
      }
    end
    context "100円玉を投入すると" do
      it "100円玉が11枚になる" do
        @vm.receive Money100
        @vm.charges.should == {
          Money10   => 10,
          Money50   => 10,
          Money100  => 11,
          Money500  => 10,
          Money1000 =>  5,
        }
      end
    end
    context "500円玉を投入してコーラを買うと" do
      it "おつり分が減る" do
        buy_cola
        @vm.charges.should == {
          Money10   =>  7,
          Money50   =>  9,
          Money100  =>  7,
          Money500  => 11,
          Money1000 =>  5,
        }
      end
    end
    context "10円玉の残りが1枚で500円玉でコーラを買うと" do
      before do
        3.times{buy_cola}
      end
      it "おつりがないので RuntimeError" do
        expect{buy_cola}.to raise_error(RuntimeError, "お釣りがありません")
        @vm.count_stock(1).should == 2
      end
    end
  end
end