Add field test gem to establish a/b testing (#6283) [deploy]

* Initial field test spec work

* Clean up specs

* Fix codeclimage

* Cleanups

* Update names

* Rename and remove need to pass logged in status

* Leadup to prod: two experiments

* Move test logic to controller and add tests

Co-authored-by: Josh Puetz <josh@grorichpuetz.com>

Gemfile

@@ -41,6 +41,7 @@ gem "fast_jsonapi", "~> 1.5" # Serializer for Ruby objects
 gem "fastly", "~> 1.15" # Client library for the Fastly acceleration system
 gem "fastly-rails", "~> 0.8" # Fastly dynamic caching integration for Rails
 gem "feedjira", "~> 3.1" # A feed fetching and parsing library
+gem "field_test", "~> 0.3" # A/B testing
 gem "figaro", "~> 1.1" # Simple, Heroku-friendly Rails app configuration using ENV and a single YAML file
 gem "fog-aws", "~> 3.5" # 'fog' gem to support Amazon Web Services
 gem "front_matter_parser", "~> 0.2" # Parse a front matter from syntactically correct strings or files

Gemfile.lock

@@ -133,6 +133,7 @@ GEM
     bootsnap (1.4.6)
       msgpack (~> 1.0)
     brakeman (4.8.0)
+    browser (2.7.1)
     buffer (0.1.3)
       addressable
       environs
@@ -223,6 +224,7 @@ GEM
       responders
       warden (~> 1.2.3)
     diff-lcs (1.3)
+    distribution (0.7.3)
     docile (1.3.2)
     dogstatsd-ruby (4.7.0)
     domain_name (0.5.20190701)
@@ -314,6 +316,11 @@ GEM
     ffi-compiler (1.0.1)
       ffi (>= 1.0.0)
       rake
+    field_test (0.3.1)
+      activerecord (>= 5)
+      browser (~> 2.0)
+      distribution
+      railties (>= 5)
     figaro (1.1.1)
       thor (~> 0.14)
     fix-db-schema-conflicts (3.0.3)
@@ -891,6 +898,7 @@ DEPENDENCIES
   fastly (~> 1.15)
   fastly-rails (~> 0.8)
   feedjira (~> 3.1)
+  field_test (~> 0.3)
   figaro (~> 1.1)
   fix-db-schema-conflicts (~> 3.0)
   fog-aws (~> 3.5)

app/controllers/stories/feeds_controller.rb

@@ -13,9 +13,27 @@ class Stories::FeedsController < ApplicationController
                 feed.top_articles_by_timeframe(timeframe: params[:timeframe])
               elsif params[:timeframe] == Timeframer::LATEST_TIMEFRAME
                 feed.latest_feed
+              elsif user_signed_in?
+                ab_test_user_signed_in_feed(feed)
               else
                 feed.default_home_feed(user_signed_in: user_signed_in?)
               end
     ArticleDecorator.decorate_collection(stories)
   end
+
+  def ab_test_user_signed_in_feed(feed)
+    test_variant = field_test(:user_home_feed, participant: current_user)
+    case test_variant
+    when "base"
+      feed.default_home_feed(user_signed_in: true)
+    when "more_random"
+      feed.default_home_feed_with_more_randomness
+    when "mix_base_and_more_random"
+      feed.mix_default_and_more_random
+    when "more_tag_weight"
+      feed.more_tag_weight
+    else
+      feed.default_home_feed(user_signed_in: true)
+    end
+  end
 end

app/models/comment.rb

@@ -20,8 +20,9 @@ class Comment < ApplicationRecord
   validates :commentable_type, inclusion: { in: %w[Article PodcastEpisode] }
   validates :user_id, presence: true
 
-  after_create   :after_create_checks
-  after_commit   :calculate_score
+  after_create :after_create_checks
+  after_create_commit :record_field_test_event
+  after_commit :calculate_score
   after_update_commit :update_notifications, if: proc { |comment| comment.saved_changes.include? "body_markdown" }
   after_save     :bust_cache
   after_save     :synchronous_bust
@@ -304,4 +305,8 @@ class Comment < ApplicationRecord
   def permissions
     errors.add(:commentable_id, "is not valid.") if commentable_type == "Article" && !commentable.published
   end
+
+  def record_field_test_event
+    Users::RecordFieldTestEventWorker.perform_async(user_id, :user_home_feed, "user_creates_comment")
+  end
 end

app/models/page_view.rb

@@ -3,6 +3,7 @@ class PageView < ApplicationRecord
   belongs_to :article
 
   before_create :extract_domain_and_path
+  after_create_commit :record_field_test_event
 
   private
 
@@ -25,4 +26,10 @@ class PageView < ApplicationRecord
   def article_tags
     article.decorate.cached_tag_list_array
   end
+
+  def record_field_test_event
+    return unless user_id
+
+    Users::RecordFieldTestEventWorker.perform_async(user_id, :user_home_feed, "user_views_article_four_days_in_week")
+  end
 end

app/models/reaction.rb

@@ -23,6 +23,7 @@ class Reaction < ApplicationRecord
   validate  :permissions
 
   before_save :assign_points
+  after_create_commit :record_field_test_event
   after_commit :async_bust, :bust_reactable_cache, :update_reactable
   after_save :index_to_algolia
   after_save :touch_user
@@ -179,4 +180,8 @@ class Reaction < ApplicationRecord
   def negative?
     category == "vomit" || category == "thumbsdown"
   end
+
+  def record_field_test_event
+    Users::RecordFieldTestEventWorker.perform_async(user_id, :user_home_feed, "user_creates_reaction")
+  end
 end

app/services/articles/feed.rb

@@ -5,6 +5,8 @@ module Articles
       @number_of_articles = number_of_articles
       @page = page
       @tag = tag
+      @randomness = 3 # default number for randomly adjusting feed
+      @tag_weight = 1 # default weight tags play in rankings
     end
 
     def published_articles_by_tag
@@ -25,28 +27,41 @@ module Articles
         page(@page).per(@number_of_articles)
     end
 
-    def default_home_feed_and_featured_story(user_signed_in: false)
-      hot_stories = published_articles_by_tag.
-        where("score > ? OR featured = ?", 9, true).
-        order("hotness_score DESC")
-      featured_story = hot_stories.where.not(main_image: nil).first
-      if user_signed_in
-        offset = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 11].sample # random offset, weighted more towards zero
-        hot_stories = hot_stories.offset(offset)
-        new_stories = Article.published.
-          where("published_at > ? AND score > ?", rand(2..6).hours.ago, -15).
-          limited_column_select.order("published_at DESC").limit(rand(15..80))
-        hot_stories = hot_stories.to_a + new_stories.to_a
-      end
-      hot_stories = rank_and_sort_articles(hot_stories) if @user
+    def default_home_feed_and_featured_story(user_signed_in: false, ranking: true)
+      featured_story, hot_stories = globally_cached_hot_articles(user_signed_in)
+      hot_stories = rank_and_sort_articles(hot_stories) if @user && ranking
       [featured_story, hot_stories]
     end
 
+    # Test variation: Base
     def default_home_feed(user_signed_in: false)
-      _featured_story, stories = default_home_feed_and_featured_story(user_signed_in: user_signed_in)
+      _featured_story, stories = default_home_feed_and_featured_story(user_signed_in: user_signed_in, ranking: true)
       stories
     end
 
+    # Test variation: More random
+    def default_home_feed_with_more_randomness
+      @randomness = 7
+      _featured_story, stories = default_home_feed_and_featured_story(user_signed_in: true)
+      stories
+    end
+
+    # Test variation: tags make bigger impact
+    def more_tag_weight
+      @tag_weight = 2
+      _featured_story, stories = default_home_feed_and_featured_story(user_signed_in: true)
+      stories
+    end
+
+    # Test variation: Base half the time, more random other half. Varies on impressions.
+    def mix_default_and_more_random
+      if rand(2) == 1
+        default_home_feed(user_signed_in: true)
+      else
+        default_home_feed_with_more_randomness
+      end
+    end
+
     def rank_and_sort_articles(articles)
       ranked_articles = articles.each_with_object({}) do |article, result|
         article_points = score_single_article(article)
@@ -76,7 +91,7 @@ module Articles
 
       article_tags = article.decorate.cached_tag_list_array
       @user.decorate.cached_followed_tags.sum do |tag|
-        article_tags.include?(tag.name) ? tag.points : 0
+        article_tags.include?(tag.name) ? tag.points * @tag_weight : 0
       end
     end
 
@@ -85,22 +100,35 @@ module Articles
     end
 
     def score_randomness
-      random_number = rand
-      if random_number < 0.3
-        3
-      elsif random_number >= 0.3 && random_number < 0.6
-        6
-      else
-        0
-      end
+      rand(3) * @randomness
     end
 
     def score_language(article)
-      @user&.preferred_languages_array&.include?(article.language || "en") ? 1 : -10
+      @user&.preferred_languages_array&.include?(article.language || "en") ? 1 : -15
     end
 
     def score_experience_level(article)
       - ((article.experience_level_rating - (@user&.experience_level || 5).abs) / 2)
     end
+
+    def globally_cached_hot_articles(user_signed_in)
+      # If these query is shared by the all users and fetched often, we can cache it and fetch cold
+      # only every x seconds.
+      Rails.cache.fetch("globally-cached-hot-articles-#{user_signed_in}", expires_in: 20.seconds) do
+        hot_stories = published_articles_by_tag.
+          where("score > ? OR featured = ?", 9, true).
+          order("hotness_score DESC")
+        featured_story = hot_stories.where.not(main_image: nil).first
+        if user_signed_in
+          offset = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 6, 7, 8, 9, 10, 11].sample # random offset, weighted more towards zero
+          hot_stories = hot_stories.offset(offset)
+          new_stories = Article.published.
+            where("published_at > ? AND score > ?", rand(2..6).hours.ago, -15).
+            limited_column_select.order("published_at DESC").limit(rand(15..80))
+          hot_stories = hot_stories.to_a + new_stories.to_a
+        end
+        [featured_story, hot_stories.to_a]
+      end
+    end
   end
 end

app/views/service_worker/index.js.erb

@@ -108,6 +108,7 @@
         !url.href.includes('/robots.txt') && // Skip robots for web crawlers
         !url.href.includes('/shell_') && // Don't fetch for shell.
         !url.href.includes('/sidekiq') && // Skip for Sidekiq dashboard
+        !url.href.includes('/abtests') && // Skip for field_test dashboard
         !url.href.includes('/social_previews') && // Skip for social previews
         !url.href.includes('/users/auth') && // Don't run on authentication.
         !url.href.includes('/enter') && // Don't run on registration.

app/workers/users/record_field_test_event_worker.rb

@@ -0,0 +1,29 @@
+module Users
+  class RecordFieldTestEventWorker
+    include Sidekiq::Worker
+    include FieldTest::Helpers
+
+    sidekiq_options queue: :low_priority, retry: 10
+
+    def perform(user_id, experiment, goal)
+      user = User.find(user_id)
+
+      if goal == "user_views_article_four_days_in_week"
+        determine_pageview_goal(user, experiment)
+      else
+        field_test_converted(experiment, participant: user, goal: goal)
+      end
+    end
+
+    private
+
+    def determine_pageview_goal(user, experiment)
+      past_week_page_view_counts = user.page_views.where("created_at > ?", 7.days.ago).
+        group("DATE(created_at)").count.values
+      past_week_page_view_counts.delete(0)
+      return unless past_week_page_view_counts.size > 3
+
+      field_test_converted(experiment, participant: user, goal: "user_views_article_four_days_in_week")
+    end
+  end
+end

config/field_test.yml

@@ -0,0 +1,25 @@
+experiments:
+  user_home_feed: # Home feed collection for logged in user
+    variants:
+      - base
+      - more_random
+      - more_tag_weight
+      - mix_base_more_random
+    weights:
+      - 65
+      - 10
+      - 10
+      - 15
+    goals:
+      - user_creates_comment
+      - user_creates_reaction
+      - user_views_article_four_days_in_week
+exclude:
+  bots: true
+
+# Dashboard performance
+cache: true
+
+# For logged-in users we'll explicitely pass participant. 
+# If we experiment on non-logged in, we don't want to collect cookies anyway.
+cookies: false

config/routes.rb

@@ -18,6 +18,7 @@ Rails.application.routes.draw do
       use Rack::Protection, origin_whitelist: ["https://dev.to"] # resolve Rack Protection HttpOrigin
     end
     mount Sidekiq::Web => "/sidekiq"
+    mount FieldTest::Engine, at: "abtests"
   end
 
   devise_scope :user do

db/migrate/20200221184007_create_field_test_memberships.rb

@@ -0,0 +1,16 @@
+class CreateFieldTestMemberships < ActiveRecord::Migration[5.2]
+  def change
+    create_table :field_test_memberships do |t|
+      t.string :participant_type
+      t.string :participant_id
+      t.string :experiment
+      t.string :variant
+      t.timestamp :created_at
+      t.boolean :converted, default: false
+    end
+
+    add_index :field_test_memberships, [:participant_type, :participant_id, :experiment],
+      unique: true, name: "index_field_test_memberships_on_participant"
+    add_index :field_test_memberships, [:experiment, :created_at]
+  end
+end

db/migrate/20200222164815_create_field_test_events.rb

@@ -0,0 +1,9 @@
+class CreateFieldTestEvents < ActiveRecord::Migration[5.2]
+  def change
+    create_table :field_test_events do |t|
+      t.references :field_test_membership
+      t.string :name
+      t.timestamp :created_at
+    end
+  end
+end

db/schema.rb

@@ -433,6 +433,24 @@ ActiveRecord::Schema.define(version: 2020_02_27_214321) do
     t.index ["reporter_id"], name: "index_feedback_messages_on_reporter_id"
   end
 
+  create_table "field_test_events", force: :cascade do |t|
+    t.datetime "created_at"
+    t.bigint "field_test_membership_id"
+    t.string "name"
+    t.index ["field_test_membership_id"], name: "index_field_test_events_on_field_test_membership_id"
+  end
+
+  create_table "field_test_memberships", force: :cascade do |t|
+    t.boolean "converted", default: false
+    t.datetime "created_at"
+    t.string "experiment"
+    t.string "participant_id"
+    t.string "participant_type"
+    t.string "variant"
+    t.index ["experiment", "created_at"], name: "index_field_test_memberships_on_experiment_and_created_at"
+    t.index ["participant_type", "participant_id", "experiment"], name: "index_field_test_memberships_on_participant", unique: true
+  end
+
   create_table "follows", id: :serial, force: :cascade do |t|
     t.boolean "blocked", default: false, null: false
     t.datetime "created_at"

spec/requests/comments_spec.rb

@@ -6,6 +6,16 @@ RSpec.describe "Comments", type: :request do
   let(:article) { create(:article, user_id: user.id) }
   let(:podcast) { create(:podcast) }
   let(:podcast_episode) { create(:podcast_episode, podcast_id: podcast.id) }
+  let(:base_comment_params) do
+    {
+      comment: {
+        commentable_id: article.id,
+        commentable_type: "Article",
+        user_id: user.id,
+        body_markdown: "New comment #{rand(10)}"
+      }
+    }
+  end
   let!(:comment) do
     create(:comment,
            commentable_id: article.id,
@@ -290,6 +300,20 @@ RSpec.describe "Comments", type: :request do
     end
   end
 
+  describe "POST /comments" do
+    context "when part of field test" do
+      before do
+        sign_in user
+        allow(Users::RecordFieldTestEventWorker).to receive(:perform_async)
+      end
+
+      it "converts field test" do
+        post "/comments", params: base_comment_params
+        expect(Users::RecordFieldTestEventWorker).to have_received(:perform_async).with(user.id, :user_home_feed, "user_creates_comment")
+      end
+    end
+  end
+
   describe "PATCH /comments/:comment_id/hide" do
     include_examples "PATCH /comments/:comment_id/hide or unhide", path: "hide", hidden: "true"
   end

spec/requests/page_views_spec.rb

@@ -37,6 +37,21 @@ RSpec.describe "PageViews", type: :request do
       end
     end
 
+    context "when part of field test" do
+      before do
+        sign_in user
+        allow(Users::RecordFieldTestEventWorker).to receive(:perform_async)
+      end
+
+      it "converts field test" do
+        post "/page_views", params: {
+          article_id: article.id,
+          referrer: "test"
+        }
+        expect(Users::RecordFieldTestEventWorker).to have_received(:perform_async).with(user.id, :user_home_feed, "user_views_article_four_days_in_week")
+      end
+    end
+
     context "when user not signed in" do
       it "creates a new page view" do
         post "/page_views", params: {

spec/requests/reactions_spec.rb

@@ -181,5 +181,17 @@ RSpec.describe "Reactions", type: :request do
         expect(Reaction.all.size).to eq(0)
       end
     end
+
+    context "when part of field test" do
+      before do
+        sign_in user
+        allow(Users::RecordFieldTestEventWorker).to receive(:perform_async)
+      end
+
+      it "converts field test" do
+        post "/reactions", params: article_params
+        expect(Users::RecordFieldTestEventWorker).to have_received(:perform_async).with(user.id, :user_home_feed, "user_creates_reaction")
+      end
+    end
   end
 end

spec/requests/stories/feeds_spec.rb

@@ -91,5 +91,25 @@ RSpec.describe "Stories::FeedsIndex", type: :request do
         expect(feed_service).to have_received(:latest_feed)
       end
     end
+
+    context "when there are no params passed (base feed) and user is signed in" do
+      before do
+        sign_in user
+      end
+
+      it "sets a field test" do
+        get "/stories/feed"
+        expect(FieldTest::Membership.all.size).to be(1)
+        expect(FieldTest::Membership.last.participant_id).to eq(user.id.to_s)
+        expect(FieldTest::Membership.last.experiment).to eq("user_home_feed")
+      end
+    end
+
+    context "when there are no params passed (base feed) and user is signed not in" do
+      it "sets a field test" do
+        get "/stories/feed"
+        expect(FieldTest::Membership.all.size).to be(0)
+      end
+    end
   end
 end

spec/services/articles/feed_spec.rb

@@ -85,6 +85,30 @@ RSpec.describe Articles::Feed, type: :service do
         expect(featured_story).to eq(hot_story)
       end
     end
+
+    context "when ranking is true" do
+      it "performs article ranking" do
+        allow(feed).to receive(:rank_and_sort_articles).and_call_original
+        feed.default_home_feed_and_featured_story(ranking: true)
+        expect(feed).to have_received(:rank_and_sort_articles)
+      end
+    end
+
+    context "when ranking is false" do
+      it "does not perform article ranking" do
+        allow(feed).to receive(:rank_and_sort_articles).and_call_original
+        feed.default_home_feed_and_featured_story(ranking: false)
+        expect(feed).not_to have_received(:rank_and_sort_articles)
+      end
+    end
+
+    context "when ranking not passed" do
+      it "performs article ranking" do
+        allow(feed).to receive(:rank_and_sort_articles).and_call_original
+        feed.default_home_feed_and_featured_story
+        expect(feed).to have_received(:rank_and_sort_articles)
+      end
+    end
   end
 
   describe "#default_home_feed" do
@@ -115,6 +139,36 @@ RSpec.describe Articles::Feed, type: :service do
     end
   end
 
+  describe "#default_home_feed_with_more_randomness" do
+    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
+    let(:stories) { feed.default_home_feed_with_more_randomness }
+
+    it "includes stories from between 2 and 6 hours ago" do
+      expect(stories).not_to include(old_story)
+      expect(stories).to include(new_story)
+    end
+  end
+
+  describe "#mix_default_and_more_random" do
+    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
+    let(:stories) { feed.mix_default_and_more_random }
+
+    it "includes stories from between 2 and 6 hours ago" do
+      expect(stories).not_to include(old_story)
+      expect(stories).to include(new_story)
+    end
+  end
+
+  describe "#more_tag_weight" do
+    let!(:new_story) { create(:article, published_at: 10.minutes.ago, score: 10) }
+    let(:stories) { feed.more_tag_weight }
+
+    it "includes stories from between 2 and 6 hours ago" do
+      expect(stories).not_to include(old_story)
+      expect(stories).to include(new_story)
+    end
+  end
+
   describe "#score_followed_user" do
     context "when article is written by a followed user" do
       before { user.follow(article.user) }
@@ -161,21 +215,21 @@ RSpec.describe Articles::Feed, type: :service do
   describe "#score_randomness" do
     context "when random number is less than 0.6 but greater than 0.3" do
       it "returns 6" do
-        allow(feed).to receive(:rand).and_return(0.5)
+        allow(feed).to receive(:rand).and_return(2)
         expect(feed.score_randomness).to eq 6
       end
     end
 
     context "when random number is less than 0.3" do
       it "returns 3" do
-        allow(feed).to receive(:rand).and_return(0.1)
+        allow(feed).to receive(:rand).and_return(1)
         expect(feed.score_randomness).to eq 3
       end
     end
 
     context "when random number is greater than 0.6" do
       it "returns 0" do
-        allow(feed).to receive(:rand).and_return(0.9)
+        allow(feed).to receive(:rand).and_return(0)
         expect(feed.score_randomness).to eq 0
       end
     end
@@ -192,7 +246,7 @@ RSpec.describe Articles::Feed, type: :service do
       before { article.language = "de" }
 
       it "returns a score of -10" do
-        expect(feed.score_language(article)).to eq(-10)
+        expect(feed.score_language(article)).to eq(-15)
       end
     end
 

spec/workers/shared_examples/enqueues_on_correct_queue.rb

@@ -2,7 +2,6 @@ RSpec.shared_examples "#enqueues_on_correct_queue" do |queue_name, args|
   describe "#perform_async" do
     it "enqueues the job" do
       Sidekiq::Testing.fake!
-
       expect do
         described_class.perform_async(args)
       end.to change { Sidekiq::Queues[queue_name].size }.by(1)

spec/workers/users/record_field_test_event_worker_spec.rb

@@ -0,0 +1,66 @@
+require "rails_helper"
+
+RSpec.describe Users::RecordFieldTestEventWorker, type: :worker do
+  include_examples "#enqueues_on_correct_queue", "low_priority", 1
+  include FieldTest::Helpers
+
+  describe "#perform" do
+    let(:worker) { subject }
+
+    let_it_be(:user) { create(:user) }
+
+    context "with user who is part of field test" do
+      before do
+        field_test(:user_home_feed, participant: user)
+      end
+
+      it "records user_creates_reaction field test conversion" do
+        worker.perform(user.id, "user_home_feed", "user_creates_reaction")
+        expect(FieldTest::Event.last.field_test_membership.participant_id).to eq(user.id.to_s)
+        expect(FieldTest::Event.last.name).to eq("user_creates_reaction")
+      end
+
+      it "records user_creates_comment field test conversion" do
+        worker.perform(user.id, "user_home_feed", "user_creates_comment")
+        expect(FieldTest::Event.last.field_test_membership.participant_id).to eq(user.id.to_s)
+        expect(FieldTest::Event.last.name).to eq("user_creates_comment")
+      end
+
+      it "records user_views_article_four_days_in_week field test conversion if qualifies" do
+        7.times do |n|
+          create(:page_view, user_id: user.id, created_at: n.day.ago)
+        end
+        worker.perform(user.id, "user_home_feed", "user_views_article_four_days_in_week")
+        expect(FieldTest::Event.last.field_test_membership.participant_id).to eq(user.id.to_s)
+        expect(FieldTest::Event.last.name).to eq("user_views_article_four_days_in_week")
+      end
+
+      it "does not record user_views_article_four_days_in_week field test conversion if not qualifying" do
+        2.times do |n|
+          create(:page_view, user_id: user.id, created_at: n.day.ago)
+        end
+        worker.perform(user.id, "user_home_feed", "user_views_article_four_days_in_week")
+        expect(FieldTest::Event.all.size).to be(0)
+      end
+    end
+
+    context "with user who is not part of field test" do
+      it "records user_creates_reaction field test conversion" do
+        worker.perform(user.id, "user_home_feed", "user_creates_reaction")
+        expect(FieldTest::Event.all.size).to be(0)
+      end
+
+      it "records user_creates_comment field test conversion" do
+        worker.perform(user.id, "user_home_feed", "user_creates_comment")
+        expect(FieldTest::Event.all.size).to be(0)
+      end
+
+      it "records user_views_article_four_days_in_week field test conversion if qualifies" do
+        7.times do |n|
+          create(:page_view, user_id: user.id, created_at: n.day.ago)
+        end
+        expect(FieldTest::Event.all.size).to be(0)
+      end
+    end
+  end
+end