Rails チュートリアル 13章 RSpecでのPost数増減のテストでDeleteが機能しない

Question

Rails チュートリアルの13章 リスト13-55においてUIに対する統合テストを初心者なりにRSpecで書いていたのですが、#destroyの部分でエラーが発生してしまいます。13章の最初からコードを見直したり、数時間調べていましたがどうにも解決しません。どうかご教示お願いします。

エラーメッセージ

Failures:

  1) microposts interface #destroy post delete post
     Failure/Error:
       expect do
         delete micropost_path(micropost)
       end.to change(Micropost, :count).by(-1)
     
       expected `Micropost.count` to have changed by -1, but was changed by 0
     # ./spec/requests/microposts_interface_spec.rb:30:in `block (3 levels) in <top (required)>'

Finished in 3.79 seconds (files took 19.72 seconds to load)
3 examples, 1 failure

Failed examples:

rspec ./spec/requests/microposts_interface_spec.rb:27 # microposts interface #destroy post delete post

test.log

[1m (0.1ms)  SELECT COUNT(*) FROM "microposts"
   (0.1ms)  SAVEPOINT active_record_1
  Micropost Create (0.2ms)  INSERT INTO "microposts" ("content", "user_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["content", "This is test post"], ["user_id", 1046959424], ["created_at", "2020-09-26 15:20:13.351638"], ["updated_at", "2020-09-26 15:20:13.351638"]]
   (5.5ms)  RELEASE SAVEPOINT active_record_1
Started DELETE "/microposts/1033843181" for 127.0.0.1 at 2020-09-27 00:20:13 +0900
Processing by MicropostsController#destroy as HTML
  Parameters: {"id"=>"1033843181"}
  User Load (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT ?  [["id", 1046959424], ["LIMIT", 1]]
  Micropost Load (0.2ms)  SELECT  "microposts".* FROM "microposts" WHERE "microposts"."user_id" = ? AND "microposts"."id" = ? ORDER BY "microposts"."created_at" DESC LIMIT ?  [["user_id", 1046959424], ["id", 1033843181], ["LIMIT", 1]]
   (0.1ms)  SAVEPOINT active_record_1
  Micropost Destroy (0.1ms)  DELETE FROM "microposts" WHERE "microposts"."id" = ?  [["id", 1033843181]]
   (0.1ms)  RELEASE SAVEPOINT active_record_1
Redirected to http://www.example.com/home
Completed 302 Found in 4ms (ActiveRecord: 0.5ms)
   (0.1ms)  SELECT COUNT(*) FROM "microposts"
   (0.4ms)  rollback transaction

/spec/requests/microposts_interface_spec.rb

require "rails_helper"

RSpec.describe "microposts interface" do
  let(:user) { create(:user) }
  let(:micropost) { user.microposts.create(content: "This is test post") }

  describe "#create post" do
    it "submit invalid post" do
      sign_in_as(user)
      visit home_path
      expect do
        post microposts_path, params: { micropost: { content: "" } }
      end.to change(Micropost, :count).by(0)
      expect(response).to render_template "static_pages/home"
    end
    it "submit valid post" do
      sign_in_as(user)
      visit home_path
      expect do
        post microposts_path, params: { micropost: { content: "This is second post" } }
      end.to change(Micropost, :count).by(1)
      expect(response).to redirect_to home_path
    end
  end

  describe "#destroy post" do
    it "delete post" do
      sign_in_as(user)
      visit home_path
      expect do
        delete micropost_path(micropost)
      end.to change(Micropost, :count).by(-1)
      expect(response).to redirect_to home_path
    end
  end

end

###microposts.controller.rb

class MicropostsController < ApplicationController
  before_action :logged_in_user, only: [:create, :destroy]
  before_action :correct_user,   only: :destroy

  def create
    @micropost = current_user.microposts.build(micropost_params)
    if @micropost.save
      flash[:success] = "Post has created"
      redirect_to home_path
    else
      @feed_items = current_user.feed.paginate(page: params[:page])
      render "static_pages/home"
    end
  end

  def destroy
    @micropost.destroy
    flash[:success] = "Your post has deleted"
    redirect_to request.referrer || home_path
  end

  private

    def micropost_params
      params.require(:micropost).permit(:content, :picture)
    end

    def correct_user
      @micropost = current_user.microposts.find_by(id: params[:id])
      if @micropost.nil?
        redirect_to home_path
      end
    end
end

###/spec/factories/users.rb

RSpec.configure do |config|
  config.include FactoryBot::Syntax::Methods
end
FactoryBot.define do
  factory :user do
    name { "Example User" }
    sequence(:email) { |n| "user_#{n}@example.com" }
    password { "password" }
    password_confirmation { "password" }
    activated {true}
    activated_at {Time.zone.now}
  end
end

補足情報（FW/ツールのバージョンなど）

source 'https://rubygems.org'

gem 'rails',        '5.2.4'
gem 'bootstrap-sass', '3.4.1'
gem 'sass-rails', '>= 3.2'
gem 'puma',         '3.9.1'
gem 'uglifier',     '3.2.0'
gem 'coffee-rails', '4.2.2'
gem 'jquery-rails', '4.3.1'
gem 'turbolinks',   '5.0.1'
gem 'jbuilder',     '2.7.0'
gem "haml-rails", "~> 2.0"
gem 'bootsnap', require: false
gem 'bcrypt',         '3.1.12'
gem 'faker',          '1.7.3'
gem 'will_paginate',           '3.1.7'
gem 'bootstrap-will_paginate', '1.0.0'
gem 'carrierwave',             '1.2.2'
gem 'mini_magick',             '4.7.0'

group :development, :test do
  gem 'sqlite3', '1.3.13'
  gem 'byebug',  '9.0.6', platform: :mri
  gem 'rspec-rails', '~> 3.8'
  gem 'spring-commands-rspec'
  gem 'capybara'
  gem 'webdrivers'
  gem 'factory_bot_rails'
  gem 'shoulda-matchers'
  gem 'rails-controller-testing'
end

group :development do
  gem 'web-console',           '3.5.1'
  gem 'listen',                '3.1.5'
  gem 'spring',                '2.0.2'
  gem 'spring-watcher-listen', '2.0.1'
end

group :test do
  gem 'minitest',                 '5.14.2'
  gem 'minitest-reporters',       '1.1.14'
  gem 'guard',                    '2.16.2'
  gem 'guard-minitest',           '2.4.4'
end

group :production do
  gem 'pg', '0.20.0'
  gem 'fog', '1.42'
end

Comments

[hatsu]

削除する前にmicropostが作られていないために0のまま７日と思いました。
let(:micropost) から let!(:micropost) のように変えてmicropostを作っておくといかがでしょうか。

[退会済みユーザー]

確かにlet!にしたところ、うまくdeleteが機能してくれました。ありがとうございます。回答の方にも書いていただくことは可能でしょうか？

Answer 1

削除する前にmicropostが作られていないために0のままのようです。

let(:micropost) から let!(:micropost) に変えて事前にmicropostを作成すると期待通り動きそうです。