CLR/H #58 で作ったコード達

fizz_buzz_counter.rb

# lib/fizz_buzz_counter.rb

class FizzBuzzCounter
  def self.filter(n)
    s = [ ['Fizz'][n % 3], ['Buzz'][n % 5] ] * ''
    s[0] ? s : n
  end

  def initialize
    @state = 0
  end

  def next
    @state += 1
    FizzBuzzCounter.filter(@state)
  end
end

fizz_buzz_counter_spec.rb

# spec/fizz_buzz_counter_spec.rb

require 'spec_helper'

describe FizzBuzzCounter do
  describe ".filter" do
    [ [ 1, 1 ],
      [ 2, 2 ],
      [ 3, 'Fizz' ],
      [ 4, 4 ],
      [ 5, 'Buzz' ],
      [ 6, 'Fizz' ],
      [ 15, 'FizzBuzz' ],
    ].each do |arg, expectation|
      context "with #{arg}" do
        it "returns #{expectation}" do
          FizzBuzzCounter.filter(arg).should be == expectation
        end
      end
    end
  end

  describe "#next" do
    context "just created" do
      subject { FizzBuzzCounter.new }

      it "calls FizzBuzzCounter.filter" do
        FizzBuzzCounter.should_receive(:filter)
        subject.next
      end

      it "calls FizzBuzzCounter.filter with 1" do
        FizzBuzzCounter.should_receive(:filter).with(1)
        subject.next
      end

      it "returns 1" do
        subject.next.should be == 1
      end
    end

    context "after called once" do
      it "return 2" do
        subject.next
        subject.next.should be == 2
      end
    end
  end
end

observer_pattern_spec.rb

# observer_pattern_spec.rb

module Observable
  def attach_observer(observer)
    observers << observer unless observers.include?(observer)
  end

  def notify
    observers.each {|ob| ob.update() }
  end

  private

  def observers
    @observers ||= []
  end
end

class ConcreteObservable
  include Observable

  def change
    notify
  end
end

describe ConcreteObservable do
  context "with an Observer" do
    subject  { ConcreteObservable.new }

    let(:observer) { double("an observer").as_null_object }

    before do
      subject.attach_observer(observer)
    end

    it "calls its notify()" do
      subject.should_receive(:notify).with()
      subject.change
    end

    it "calls observer's update()" do
      observer.should_receive(:update).with()
      subject.change
    end
  end
end

spec_helper.rb

# spec/spec_helper.rb

$LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
require 'fizz_buzz_counter'