テスト駆動開発入門をRubyで写経してみた。6

6章で実施したこと

• Franc、Dollarの親クラスMoneyの追加
• Franc、Dollarの*()メソッドをMoneyに移動

money.rb

#!/usr/bin/ruby
#coding: utf-8
# テスト駆動開発入門6章 再度、すべてに対する等価性
class Money
  attr_accessor :amount
  protected :amount

  def ==(other)
    return @amount == other.amount
  end
end

class Dollar < Money
  def initialize(amount)
    @amount = amount
  end

  def *(multiplier)
    return Dollar.new(@amount * multiplier)
  end
end

class Franc < Money
  def initialize(amount)
    @amount = amount
  end

  def *(multiplier)
    return Franc.new(@amount * multiplier)
  end
end

money_test.rb

#!/usr/bin/ruby
#coding: utf-8
# テスト駆動開発入門6章 再度、すべてに対する等価性
require 'test/unit'
require 'money'

class TestMoney < Test::Unit::TestCase
  def test_multiplication
    five = Dollar.new(5)
    assert_equal(Dollar.new(10), five * 2)
    assert_equal(Dollar.new(15), five * 3)
  end

  def test_equality
    assert(Dollar.new(5) == Dollar.new(5))
    assert(Dollar.new(5) != Dollar.new(6))
    assert(Franc.new(5)  == Franc.new(5))
    assert(Franc.new(5)  != Franc.new(6))
  end

  def test_Franc_multiplication
    five = Franc.new(5)
    assert_equal(Franc.new(10), five * 2)
    assert_equal(Franc.new(15), five * 3)
  end
end