Setup benchmarking structure

- Setup dummy app files in `test/dummy`
- Setup dummy test server `bin/serve_dummy
  - Note:  Serializer caching can be completely disabled by passing in
  `CACHE_ON=off bin/serve_dummy start` since Serializer#_cache is only
  set at boot.
- run with
  - ./bin/bench
  - `bin/bench` etc adapted from ruby-bench-suite
  - target files are `test/dummy/bm_*.rb`. Just add another to run it.
  - benchmark cache/no cache
  - remove rake dependency that loads unnecessary files
- remove git gem dependency
  - Running over revisions to be added in subsequent PR

.rubocop.yml

@@ -1,6 +1,7 @@
 inherit_from: .rubocop_todo.yml
 
 AllCops:
+  TargetRubyVersion: 2.2
   Exclude:
     - config/initializers/forbidden_yaml.rb
     - !ruby/regexp /(vendor|bundle|bin|db|tmp)\/.*/

Gemfile

@@ -36,6 +36,11 @@ end
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem 'tzinfo-data', platforms: (@windows_platforms + [:jruby])
 
+group :bench do
+  # https://github.com/rails-api/active_model_serializers/commit/cb4459580a6f4f37f629bf3185a5224c8624ca76
+  gem 'benchmark-ips', require: false, group: :development
+end
+
 group :test do
   gem 'sqlite3',                          platform: (@windows_platforms + [:ruby])
   gem 'activerecord-jdbcsqlite3-adapter', platform: :jruby
@@ -45,5 +50,4 @@ end
 
 group :development, :test do
   gem 'rubocop', '~> 0.36', require: false
-  gem 'git'
 end

Rakefile

@@ -74,38 +74,3 @@ end
 
 desc 'CI test task'
 task :ci => [:default]
-
-require 'git'
-require 'benchmark'
-Rake::TestTask.new :benchmark_tests do |t|
-  t.libs << "test"
-  t.test_files = FileList['test/**/*_benchmark.rb']
-  t.ruby_opts = ['-r./test/test_helper.rb']
-  t.verbose = true
-end
-
-task :benchmark do
-  @git = Git.init('.')
-  ref  = @git.current_branch
-
-  actual = run_benchmark_spec ref
-  master = run_benchmark_spec 'master'
-
-  @git.checkout(ref)
-
-  puts "\n\nResults ============================\n"
-  puts "------------------------------------~> (Branch) MASTER"
-  puts master
-  puts "------------------------------------\n\n"
-
-  puts "------------------------------------~> (Actual Branch) #{ref}"
-  puts actual
-  puts "------------------------------------"
-end
-
-def run_benchmark_spec(ref)
-  @git.checkout(ref)
-  response = Benchmark.realtime { Rake::Task['benchmark_tests'].invoke }
-  Rake::Task['benchmark_tests'].reenable
-  response
-end

active_model_serializers.gemspec

@@ -17,6 +17,7 @@ Gem::Specification.new do |spec|
   spec.files         = `git ls-files -z`.split("\x0")
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
+  spec.executables   = []
 
   spec.required_ruby_version = '>= 2.0.0'
 

bin/bench

@@ -0,0 +1,170 @@
+#!/usr/bin/env ruby
+# ActiveModelSerializers Benchmark driver
+# Adapted from
+# https://github.com/ruby-bench/ruby-bench-suite/blob/8ad567f7e43a044ae48c36833218423bb1e2bd9d/rails/benchmarks/driver.rb
+require 'bundler'
+Bundler.setup
+require 'json'
+require 'pathname'
+require 'optparse'
+require 'digest'
+require 'pathname'
+require 'shellwords'
+require 'logger'
+require 'English'
+
+class BenchmarkDriver
+  ROOT = Pathname File.expand_path(File.join('..', '..'), __FILE__)
+  BASE = ENV.fetch('BASE') { ROOT.join('test', 'dummy') }
+  ESCAPED_BASE = Shellwords.shellescape(BASE)
+
+  def self.benchmark(options)
+    new(options).run
+  end
+
+  def self.parse_argv_and_run(argv = ARGV, options = {})
+    options = {
+      repeat_count: 1,
+      pattern: [],
+      env: 'CACHE_ON=on'
+    }.merge!(options)
+
+    OptionParser.new do |opts|
+      opts.banner = 'Usage: bin/bench [options]'
+
+      opts.on('-r', '--repeat-count [NUM]', 'Run benchmarks [NUM] times taking the best result') do |value|
+        options[:repeat_count] = value.to_i
+      end
+
+      opts.on('-p', '--pattern <PATTERN1,PATTERN2,PATTERN3>', 'Benchmark name pattern') do |value|
+        options[:pattern] = value.split(',')
+      end
+
+      opts.on('-e', '--env <var1=val1,var2=val2,var3=vale>', 'ENV variables to pass in') do |value|
+        options[:env] = value.split(',')
+      end
+    end.parse!(argv)
+
+    benchmark(options)
+  end
+
+  attr_reader :commit_hash, :base
+
+  # Based on logfmt:
+  # https://www.brandur.org/logfmt
+  # For more complete implementation see:
+  # see https://github.com/arachnid-cb/logfmtr/blob/master/lib/logfmtr/base.rb
+  # For usage see:
+  # https://blog.codeship.com/logfmt-a-log-format-thats-easy-to-read-and-write/
+  # https://engineering.heroku.com/blogs/2014-09-05-hutils-explore-your-structured-data-logs/
+  # For Ruby parser see:
+  # https://github.com/cyberdelia/logfmt-ruby
+  def self.summary_logger(device = 'output.txt')
+    require 'time'
+    logger = Logger.new(device)
+    logger.level = Logger::INFO
+    logger.formatter = proc { |severity, datetime, progname, msg|
+      msg = "'#{msg}'"
+      "level=#{severity} time=#{datetime.utc.iso8601(6)} pid=#{Process.pid} progname=#{progname} msg=#{msg}#{$INPUT_RECORD_SEPARATOR}"
+    }
+    logger
+  end
+
+  def self.stdout_logger
+    logger = Logger.new(STDOUT)
+    logger.level = Logger::INFO
+    logger.formatter = proc { |_, _, _, msg| "#{msg}#{$INPUT_RECORD_SEPARATOR}" }
+    logger
+  end
+
+  def initialize(options)
+    @writer       = ENV['SUMMARIZE'] ? self.class.summary_logger : self.class.stdout_logger
+    @repeat_count = options[:repeat_count]
+    @pattern      = options[:pattern]
+    @commit_hash  = options.fetch(:commit_hash) { `git rev-parse --short HEAD`.chomp }
+    @base         = options.fetch(:base) { ESCAPED_BASE }
+    @env          = Array(options[:env]).join(' ')
+    @rubyopt = options[:rubyopt] # TODO: rename
+  end
+
+  def run
+    files.each do |path|
+      next if !@pattern.empty? && /#{@pattern.join('|')}/ !~ File.basename(path)
+      run_single(Shellwords.shellescape(path))
+    end
+  end
+
+  private
+
+  def files
+    Dir[File.join(base, 'bm_*')]
+  end
+
+  def run_single(path)
+    script = "RAILS_ENV=production #{@env} ruby #{@rubyopt} #{path}"
+    environment = `ruby -v`.chomp.strip[/\d+\.\d+\.\d+\w+/]
+
+    runs_output = measure(script)
+    if runs_output.empty?
+      results = { error: :no_results }
+      return
+    end
+
+    results = {}
+    results['commit_hash'] = commit_hash
+    results['version'] = runs_output.first['version']
+    results['benchmark_run[environment]'] = environment
+    results['runs'] = []
+
+    runs_output.each do |output|
+      results['runs'] << {
+        'benchmark_type[category]' => output['label'],
+        'benchmark_run[result][iterations_per_second]' => output['iterations_per_second'].round(3),
+        'benchmark_run[result][total_allocated_objects_per_iteration]' => output['total_allocated_objects_per_iteration']
+      }
+    end
+  ensure
+    results && report(results)
+  end
+
+  def report(results)
+    @writer.info { 'Benchmark results:' }
+    @writer.info { JSON.pretty_generate(results) }
+  end
+
+  def summarize(result)
+    puts "#{result['label']} #{result['iterations_per_second']}/ips; #{result['total_allocated_objects_per_iteration']} objects"
+  end
+
+  # FIXME: ` provides the full output but it'll return failed output as well.
+  def measure(script)
+    results = Hash.new { |h, k| h[k] = [] }
+
+    @repeat_count.times do
+      output = sh(script)
+      output.each_line do |line|
+        next if line.nil?
+        begin
+          result = JSON.parse(line)
+        rescue JSON::ParserError
+          result = { error: line } # rubocop:disable Lint/UselessAssignment
+        else
+          summarize(result)
+          results[result['label']] << result
+        end
+      end
+    end
+
+    results.map do |_, bm_runs|
+      bm_runs.sort_by do |run|
+        run['iterations_per_second']
+      end.last
+    end
+  end
+
+  def sh(cmd)
+    `#{cmd}`
+  end
+end
+
+BenchmarkDriver.parse_argv_and_run if $PROGRAM_NAME == __FILE__

bin/serve_dummy

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -e
+
+case "$1" in
+
+  start)
+  config="${CONFIG_RU:-test/dummy/config.ru}"
+  bundle exec ruby -Ilib -S rackup "$config" --daemonize --pid tmp/dummy_app.pid --warn --server webrick
+  until [ -f 'tmp/dummy_app.pid' ]; do
+    sleep 0.1 # give it time to start.. I don't know a better way
+  done
+  cat tmp/dummy_app.pid
+  true
+  ;;
+
+  stop)
+  if [ -f 'tmp/dummy_app.pid' ]; then
+    kill -TERM $(cat tmp/dummy_app.pid)
+  else
+    echo 'No pidfile'
+    false
+  fi
+  ;;
+
+  status)
+  if [ -f 'tmp/dummy_app.pid' ]; then
+    kill -0 $(cat tmp/dummy_app.pid)
+    [ "$?" -eq 0 ]
+  else
+    echo 'No pidfile'
+    false
+  fi
+  ;;
+
+  *)
+  echo "Usage: $0 [start|stop|status]"
+  ;;
+
+esac

test/benchmark/serialization_benchmark.rb

@@ -1,50 +0,0 @@
-require 'test_helper'
-
-module ActionController
-  module Serialization
-    class SerializerTest < ActionController::TestCase
-      class PostController < ActionController::Base
-
-        def render_with_cache_enable
-          comment = Comment.new({ id: 1, body: 'ZOMG A COMMENT' })
-          author  = Author.new(id: 1, name: 'Joao Moura.')
-          post    = Post.new({ id: 1, title: 'New Post', blog:nil, body: 'Body', comments: [comment], author: author })
-
-          render json: post
-        end
-      end
-
-      tests PostController
-
-      def test_render_with_cache_enable
-        ActionController::Base.cache_store.clear
-        get :render_with_cache_enable
-
-        expected = {
-          id: 1,
-          title: 'New Post',
-          body: 'Body',
-          comments: [
-            {
-              id: 1,
-              body: 'ZOMG A COMMENT' }
-          ],
-          blog: {
-            id: 999,
-            name: 'Custom blog'
-          },
-          author: {
-            id: 1,
-            name: 'Joao Moura.'
-          }
-        }
-
-        assert_equal 'application/json', @response.content_type
-        assert_equal expected.to_json, @response.body
-
-        get :render_with_cache_enable
-        assert_equal expected.to_json, @response.body
-      end
-    end
-  end
-end

test/dummy/app.rb

@@ -0,0 +1,65 @@
+# https://github.com/rails-api/active_model_serializers/pull/872
+# approx ref 792fb8a9053f8db3c562dae4f40907a582dd1720 to test against
+require 'bundler/setup'
+
+require 'rails'
+require 'active_model'
+require 'active_support'
+require 'active_support/json'
+require 'action_controller'
+require 'action_controller/test_case'
+require 'action_controller/railtie'
+abort "Rails application already defined: #{Rails.application.class}" if Rails.application
+
+class NullLogger < Logger
+  def initialize(*_args)
+  end
+
+  def add(*_args, &_block)
+  end
+end
+class DummyLogger < ActiveSupport::Logger
+  def initialize
+    @file = StringIO.new
+    super(@file)
+  end
+
+  def messages
+    @file.rewind
+    @file.read
+  end
+end
+# ref: https://gist.github.com/bf4/8744473
+class DummyApp < Rails::Application
+  # Set up production configuration
+  config.eager_load = true
+  config.cache_classes = true
+  # CONFIG: CACHE_ON={on,off}
+  config.action_controller.perform_caching = ENV['CACHE_ON'] != 'off'
+  config.action_controller.cache_store = ActiveSupport::Cache.lookup_store(:memory_store)
+
+  config.active_support.test_order = :random
+  config.secret_token = 'S' * 30
+  config.secret_key_base = 'abc123'
+  config.consider_all_requests_local = false
+
+  # otherwise deadlock occured
+  config.middleware.delete 'Rack::Lock'
+
+  # to disable log files
+  config.logger = NullLogger.new
+  config.active_support.deprecation = :log
+  config.log_level = :info
+end
+
+require 'active_model_serializers'
+
+# Initialize app before any serializers are defined, for running across revisions.
+# ref: https://github.com/rails-api/active_model_serializers/pull/1478
+Rails.application.initialize!
+# HACK: Serializer::cache depends on the ActionController-dependent configs being set.
+ActiveSupport.on_load(:action_controller) do
+  require_relative 'fixtures'
+end
+
+require_relative 'controllers'

test/dummy/benchmarking_support.rb

@@ -0,0 +1,66 @@
+require 'benchmark/ips'
+require 'json'
+
+# Add benchmarking runner from ruby-bench-suite
+# https://github.com/ruby-bench/ruby-bench-suite/blob/master/rails/benchmarks/support/benchmark_rails.rb
+module Benchmark
+  module ActiveModelSerializers
+    module TestMethods
+      def request(method, path)
+        response = Rack::MockRequest.new(DummyApp).send(method, path)
+        if response.status.in?([404, 500])
+          fail "omg, #{method}, #{path}, '#{response.status}', '#{response.body}'"
+        end
+        response
+      end
+    end
+
+    # extend Benchmark with an `ams` method
+    def ams(label = nil, time:, disable_gc: true, warmup: 3, &block)
+      fail ArgumentError.new, 'block should be passed' unless block_given?
+
+      if disable_gc
+        GC.disable
+      else
+        GC.enable
+      end
+
+      report = Benchmark.ips(time, warmup, true) do |x|
+        x.report(label) { yield }
+      end
+
+      entry = report.entries.first
+
+      output = {
+        label: label,
+        version: ::ActiveModel::Serializer::VERSION.to_s,
+        iterations_per_second: entry.ips,
+        iterations_per_second_standard_deviation: entry.stddev_percentage,
+        total_allocated_objects_per_iteration: count_total_allocated_objects(&block)
+      }.to_json
+
+      puts output
+      output
+    end
+
+    def count_total_allocated_objects
+      if block_given?
+        key =
+          if RUBY_VERSION < '2.2'
+            :total_allocated_object
+          else
+            :total_allocated_objects
+          end
+
+        before = GC.stat[key]
+        yield
+        after = GC.stat[key]
+        after - before
+      else
+        -1
+      end
+    end
+  end
+
+  extend Benchmark::ActiveModelSerializers
+end

test/dummy/bm_caching.rb

@@ -0,0 +1,116 @@
+require_relative './benchmarking_support'
+require_relative './app'
+
+# https://github.com/ruby-bench/ruby-bench-suite/blob/8ad567f7e43a044ae48c36833218423bb1e2bd9d/rails/benchmarks/actionpack_router.rb
+class ApiAssertion
+  include Benchmark::ActiveModelSerializers::TestMethods
+  BadRevisionError = Class.new(StandardError)
+
+  def valid?
+    caching = get_caching
+    caching[:body].delete('meta')
+    non_caching = get_non_caching
+    non_caching[:body].delete('meta')
+    assert_responses(caching, non_caching)
+  rescue BadRevisionError => e
+    msg = { error: e.message }
+    STDERR.puts msg
+    STDOUT.puts msg
+    exit 1
+  end
+
+  def get_status(on_off = 'on'.freeze)
+    get("/status/#{on_off}")
+  end
+
+  def clear
+    get('/clear')
+  end
+
+  def get_caching(on_off = 'on'.freeze)
+    get("/caching/#{on_off}")
+  end
+
+  def get_non_caching(on_off = 'on'.freeze)
+    get("/non_caching/#{on_off}")
+  end
+
+  private
+
+  def assert_responses(caching, non_caching)
+    assert_equal(caching[:code], 200, "Caching response failed: #{caching}")
+    assert_equal(caching[:body], expected, "Caching response format failed: \n+ #{caching[:body]}\n- #{expected}")
+    assert_equal(caching[:content_type], 'application/json; charset=utf-8', "Caching response content type  failed: \n+ #{caching[:content_type]}\n- application/json")
+    assert_equal(non_caching[:code], 200, "Non caching response failed: #{non_caching}")
+    assert_equal(non_caching[:body], expected, "Non Caching response format failed: \n+ #{non_caching[:body]}\n- #{expected}")
+    assert_equal(non_caching[:content_type], 'application/json; charset=utf-8', "Non caching response content type  failed: \n+ #{non_caching[:content_type]}\n- application/json")
+  end
+
+  def get(url)
+    response = request(:get, url)
+    { code: response.status, body: JSON.load(response.body), content_type: response.content_type }
+  end
+
+  def expected
+    @expected ||=
+      {
+        'post' =>  {
+          'id' =>  1337,
+          'title' => 'New Post',
+          'body' =>  'Body',
+          'comments' => [
+            {
+              'id' => 1,
+              'body' => 'ZOMG A COMMENT'
+            }
+          ],
+          'blog' =>  {
+            'id' =>  999,
+            'name' => 'Custom blog'
+          },
+          'author' => {
+            'id' => 42,
+            'name' => 'Joao Moura.'
+          }
+        }
+    }
+  end
+
+  def assert_equal(expected, actual, message)
+    return true if expected == actual
+    if ENV['FAIL_ASSERTION'] =~ /\Atrue|on|0\z/i # rubocop:disable Style/GuardClause
+      fail BadRevisionError, message
+    else
+      STDERR.puts message unless ENV['SUMMARIZE']
+    end
+  end
+
+  def debug(msg = '')
+    if block_given? && ENV['DEBUG'] =~ /\Atrue|on|0\z/i
+      STDERR.puts yield
+    else
+      STDERR.puts msg
+    end
+  end
+end
+assertion = ApiAssertion.new
+assertion.valid?
+# STDERR.puts assertion.get_status
+
+time = 10
+{
+  'caching on: caching serializers: gc off' => { disable_gc: true, send: [:get_caching, 'on'] },
+  # 'caching on: caching serializers: gc on' => { disable_gc: false, send: [:get_caching, 'on'] },
+  'caching off: caching serializers: gc off' => { disable_gc: true, send: [:get_caching, 'off'] },
+  # 'caching off: caching serializers: gc on' => { disable_gc: false, send: [:get_caching, 'off'] },
+  'caching on: non-caching serializers: gc off' => { disable_gc: true, send: [:get_non_caching, 'on'] },
+  # 'caching on: non-caching serializers: gc on' => { disable_gc: false, send: [:get_non_caching, 'on'] },
+  'caching off: non-caching serializers: gc off' => { disable_gc: true, send: [:get_non_caching, 'off'] }
+  # 'caching off: non-caching serializers: gc on' => { disable_gc: false, send: [:get_non_caching, 'off'] }
+}.each do |label, options|
+  assertion.clear
+  Benchmark.ams(label, time: time, disable_gc: options[:disable_gc]) do
+    assertion.send(*options[:send])
+  end
+  # STDERR.puts assertion.get_status(options[:send][-1])
+end

test/dummy/config.ru

@@ -0,0 +1,3 @@
+require File.expand_path(['..', 'app'].join(File::SEPARATOR), __FILE__)
+
+run Rails.application

test/dummy/controllers.rb

@@ -0,0 +1,77 @@
+class PostController < ActionController::Base
+  POST =
+    begin
+      if ENV['BENCH_STRESS']
+        comments = (0..50).map do |i|
+          Comment.new(id: i, body: 'ZOMG A COMMENT')
+        end
+      else
+        comments = [Comment.new(id: 1, body: 'ZOMG A COMMENT')]
+      end
+      author = Author.new(id: 42, name: 'Joao Moura.')
+      Post.new(id: 1337, title: 'New Post', blog: nil, body: 'Body', comments: comments, author: author)
+    end
+
+  def render_with_caching_serializer
+    toggle_cache_status
+    render json: POST, serializer: CachingPostSerializer, adapter: :json, meta: { caching: perform_caching }
+  end
+
+  def render_with_non_caching_serializer
+    toggle_cache_status
+    render json: POST, adapter: :json, meta: { caching: perform_caching }
+  end
+
+  def render_cache_status
+    toggle_cache_status
+    # Uncomment to debug
+    # STDERR.puts cache_store.class
+    # STDERR.puts cache_dependencies
+    # ActiveSupport::Cache::Store.logger.debug [ActiveModelSerializers.config.cache_store, ActiveModelSerializers.config.perform_caching, CachingPostSerializer._cache, perform_caching, params].inspect
+    render json: { caching: perform_caching, meta: { cache_log: cache_messages, cache_status: cache_status } }.to_json
+  end
+
+  def clear
+    ActionController::Base.cache_store.clear
+    # Test caching is on
+    # Uncomment to turn on logger; possible performance issue
+    # logger = DummyLogger.new
+    # ActiveSupport::Cache::Store.logger = logger # seems to be the best way
+    #
+    # the below is used in some rails tests but isn't available/working in all versions, so far as I can tell
+    # https://github.com/rails/rails/pull/15943
+    # ActiveSupport::Notifications.subscribe(/^cache_(.*)\.active_support$/) do |*args|
+    #   logger.debug ActiveSupport::Notifications::Event.new(*args)
+    # end
+    render json: 'ok'.to_json
+  end
+
+  private
+
+  def cache_status
+    {
+      controller: perform_caching,
+      app: Rails.configuration.action_controller.perform_caching,
+      serializers: Rails.configuration.serializers.each_with_object({}) { |serializer, data| data[serializer.name] = serializer._cache.present? }
+    }
+  end
+
+  def cache_messages
+    ActiveSupport::Cache::Store.logger.is_a?(DummyLogger) && ActiveSupport::Cache::Store.logger.messages.split("\n")
+  end
+
+  def toggle_cache_status
+    case params[:on]
+    when 'on'.freeze then self.perform_caching = true
+    when 'off'.freeze then self.perform_caching = false
+    else nil # no-op
+    end
+  end
+end
+
+Rails.application.routes.draw do
+  get '/status(/:on)' => 'post#render_cache_status'
+  get '/clear' => 'post#clear'
+  get '/caching(/:on)' => 'post#render_with_caching_serializer'
+  get '/non_caching(/:on)' => 'post#render_with_non_caching_serializer'
+end

test/dummy/fixtures.rb

@@ -0,0 +1,157 @@
+Rails.configuration.serializers = []
+class AuthorSerializer < ActiveModel::Serializer
+  attributes :id, :name
+
+  has_many :posts, embed: :ids
+  has_one :bio
+end
+Rails.configuration.serializers << AuthorSerializer
+
+class BlogSerializer < ActiveModel::Serializer
+  attributes :id, :name
+end
+Rails.configuration.serializers << BlogSerializer
+
+class CommentSerializer < ActiveModel::Serializer
+  attributes :id, :body
+
+  belongs_to :post
+  belongs_to :author
+end
+Rails.configuration.serializers << CommentSerializer
+
+class PostSerializer < ActiveModel::Serializer
+  attributes :id, :title, :body
+
+  has_many :comments, serializer: CommentSerializer
+  belongs_to :blog, serializer: BlogSerializer
+  belongs_to :author, serializer: AuthorSerializer
+
+  def blog
+    Blog.new(id: 999, name: 'Custom blog')
+  end
+end
+Rails.configuration.serializers << PostSerializer
+
+class CachingAuthorSerializer < AuthorSerializer
+  cache key: 'writer', only: [:name], skip_digest: true
+end
+Rails.configuration.serializers << CachingAuthorSerializer
+
+class CachingCommentSerializer < CommentSerializer
+  cache expires_in: 1.day, skip_digest: true
+end
+Rails.configuration.serializers << CachingCommentSerializer
+
+class CachingPostSerializer < PostSerializer
+  cache key: 'post', expires_in: 0.1, skip_digest: true
+  belongs_to :blog, serializer: BlogSerializer
+  belongs_to :author, serializer: CachingAuthorSerializer
+  has_many :comments, serializer: CachingCommentSerializer
+end
+Rails.configuration.serializers << CachingPostSerializer
+
+if ENV['ENABLE_ACTIVE_RECORD'] == 'true'
+  require 'active_record'
+
+  ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
+  ActiveRecord::Schema.define do
+    self.verbose = false
+
+    create_table :blogs, force: true do |t|
+      t.string :name
+      t.timestamps null: false
+    end
+    create_table :authors, force: true do |t|
+      t.string :name
+      t.timestamps null: false
+    end
+    create_table :posts, force: true do |t|
+      t.string :title
+      t.text :body
+      t.references :author
+      t.references :blog
+      t.timestamps null: false
+    end
+    create_table :comments, force: true do |t|
+      t.text :body
+      t.references :author
+      t.references :post
+      t.timestamps null: false
+    end
+  end
+
+  class Comment < ActiveRecord::Base
+    belongs_to :author
+    belongs_to :post
+  end
+
+  class Author < ActiveRecord::Base
+    has_many :posts
+    has_many :comments
+  end
+
+  class Post < ActiveRecord::Base
+    has_many :comments
+    belongs_to :author
+    belongs_to :blog
+  end
+
+  class Blog < ActiveRecord::Base
+    has_many :posts
+  end
+else
+  # ActiveModelSerializers::Model is a convenient
+  # serializable class to inherit from when making
+  # serializable non-activerecord objects.
+  class DummyModel
+    include ActiveModel::Model
+    include ActiveModel::Serializers::JSON
+
+    attr_reader :attributes
+
+    def initialize(attributes = {})
+      @attributes = attributes
+      super
+    end
+
+    # Defaults to the downcased model name.
+    def id
+      attributes.fetch(:id) { self.class.name.downcase }
+    end
+
+    # Defaults to the downcased model name and updated_at
+    def cache_key
+      attributes.fetch(:cache_key) { "#{self.class.name.downcase}/#{id}" }
+    end
+
+    # Defaults to the time the serializer file was modified.
+    def updated_at
+      @updated_at ||= attributes.fetch(:updated_at) { File.mtime(__FILE__) }
+    end
+
+    def read_attribute_for_serialization(key)
+      if key == :id || key == 'id'
+        attributes.fetch(key) { id }
+      else
+        attributes[key]
+      end
+    end
+  end
+
+  class Comment < DummyModel
+    attr_accessor :id, :body
+  end
+
+  class Author < DummyModel
+    attr_accessor :id, :name, :posts
+  end
+
+  class Post < DummyModel
+    attr_accessor :id, :title, :body, :comments, :blog, :author
+  end
+
+  class Blog < DummyModel
+    attr_accessor :id, :name
+  end
+end