fakes3 と fakefs で Amazon S3 連携のテストを書いてみた

s3 = AWS::S3.new(
  :access_key_id       => 'YOUR_ACCESS_KEY_ID',
  :secret_access_key   => 'YOUR_SECRET_ACCESS_KEY',
  :s3_endpoint         => 'localhost',
  :s3_force_path_style => true,
  :s3_port             => 12345,
  :use_ssl             => false
)

s3 = AWS::S3.new(
  :access_key_id       => 'YOUR_ACCESS_KEY_ID',
  :secret_access_key   => 'YOUR_SECRET_ACCESS_KEY',
  :s3_endpoint         => 'lvh.me',
  :s3_port             => 12345,
  :use_ssl             => false
)

FakeS3::Server.new('0.0.0.0', 12345, FakeS3::FileStore.new('/tmp/fakes3'), 'localhost').serve

require 'spec_helper'
require 'fakefs/spec_helpers'

describe SomeClass do
  describe '#some_method' do
    include FakeFS::SpecHelpers

    it '...' do
      ...
    end
  end
end

require 'fakefs/safe'

module Kernel
  alias_method :require_with_fakefs, :require

  def require_without_fakefs(path)
    FakeFS.without { require_with_fakefs(path) }
  end
  alias_method :require, :require_without_fakefs
end

FakeFS.activate!

require "s3_downloader/version"
require 'aws-sdk'

module S3Downloader
  BUCKET_NAME = 'test'
  DOWNLOAD_DIR = '/path/to/Downloads'

  class << self
    def download_all
      s3.buckets[BUCKET_NAME].objects.each do |object|
        File.open(File.join(DOWNLOAD_DIR, object.key), 'wb') do |file|
          object.read do |chunk|
            file.write(chunk)
          end
        end
      end
    end

    private

    def s3
      @s3 ||= AWS::S3.new(
        :access_key_id     => ENV['AWS_ACCESS_KEY_ID'],
        :secret_access_key => ENV['AWS_SECRET_ACCESS_KEY'],
      )
    end
  end
end

# coding: utf-8
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 's3_downloader/version'

Gem::Specification.new do |spec|
  spec.name          = "s3_downloader"
  spec.version       = S3Downloader::VERSION
  spec.authors       = ["a_bicky"]
  spec.email         = ["a_bicky@example.com"]
  spec.description   = %q{TODO: Write a gem description}
  spec.summary       = %q{TODO: Write a gem summary}
  spec.homepage      = ""
  spec.license       = "MIT"

  spec.files         = `git ls-files`.split($/)
  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
  spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
  spec.require_paths = ["lib"]

  spec.add_dependency "aws-sdk", "~> 1.51.0"
  spec.add_development_dependency "bundler", "~> 1.3"
  spec.add_development_dependency "rake"
  spec.add_development_dependency "rspec"
  spec.add_development_dependency "fakefs"
  spec.add_development_dependency "fakes3"
end

# spec/s3_downloader_spec.rb
require 'spec_helper'
require 'fakes3/server'
require 'fakefs/spec_helpers'

describe S3Downloader do
  PORT = 12345

  before(:all) do
    # bundle exec rake spec だと何故かこれがなくても動く（rake spec だと必要）
    # module Kernel
    #   alias_method :require_with_fakefs, :require
    #
    #   def require_without_fakefs(path)
    #     FakeFS.without { require_with_fakefs(path) }
    #   end
    #   alias_method :require, :require_without_fakefs
    # end

    # fakes3 のサーバを起動。テストが終了した時にシグナルを送ることでサーバを落とす。
    pid = Process.fork do
      Dir.mktmpdir do |dir|
        def $stderr.write(*args); end  # Suppress outputs
        FakeS3::Server.new('0.0.0.0', PORT, FakeS3::FileStore.new(dir), 'localhost').serve
      end
    end
    at_exit do
      Process.kill(:TERM, pid)
    end
  end

  describe '.download_all' do
    include FakeFS::SpecHelpers

    # S3Downloader.s3 を stub することで fakes3 に対してリクエストを送る
    let(:s3) do
      AWS::S3.new(
        :access_key_id       => 'access_key',
        :secret_access_key   => 'secret_access',
        :s3_endpoint         => 'localhost',
        :s3_port             => PORT,
        :s3_force_path_style => true,
        :use_ssl             => false,
      )
    end
    let(:objects) do
      [{ :key => 'foo', :value => 'bar' }, { :key => 'hoge', :value => 'fuga' }]
    end
    before do
      FileUtils.mkdir_p(S3Downloader::DOWNLOAD_DIR)
      # ダウンロードするためのファイルを作成
      objects.each do |obj|
        s3.buckets[S3Downloader::BUCKET_NAME].objects.create(obj[:key], obj[:value])
      end
      allow(S3Downloader).to receive(:s3) { s3 }
    end

    it 'downloads files' do
      objects.each do |obj|
        expect(File.exists?(File.join(S3Downloader::DOWNLOAD_DIR, obj[:key]))).to be false
      end

      S3Downloader.download_all

      objects.each do |obj|
        expect(File.read(File.join(S3Downloader::DOWNLOAD_DIR, obj[:key]))).to eq obj[:value]
      end
    end
  end
end

[1] pry(main)> require 'aws-sdk'
=> true
[2] pry(main)> AWS.stub!
=> nil
[3] pry(main)> s3 = AWS::S3.new(:access_key_id => 'key', :secret_access_key => 'secret')
=> <AWS::S3>
[4] pry(main)> obj = s3.buckets['test'].objects.create('key', 'value')
=> <AWS::S3::S3Object:test/key>
[5] pry(main)> obj.key
=> "key"
[6] pry(main)> obj.read  # 'value' が返ってほしい
=> nil
[7] pry(main)> obj.content_length  # 'value'.length が返ってほしい
=> nil

[8] pry(main)> response = s3.client.stub_for(:get_object)
=> {}
[9] pry(main)> response[:data] = 'value'
=> "value"
[10] pry(main)> obj.read
=> "value"
[11] pry(main)> response = s3.client.stub_for(:head_object)
=> {}
[12] pry(main)> response[:content_length] = 'value'.length
=> 5
[13] pry(main)> obj.content_length
=> 5

def stub_for method_name
  @stubs ||= {}
  @stubs[method_name] ||= new_stub_for(method_name)
end