Rspec view неопределенный метод stub_model

Я пытаюсь выяснить, что не так с этим кодом. А именно, он не может найти метод 'stub_model'. Пытался найти решение для этого, но везде я смотрю мои файлы, кажется, хорошо. Пожалуйста, взгляните на это, может быть, я просто не вижу простой ошибки. Большое спасибо :) Модель книги создана в БД.

Моя спецификация представления (spec / view / books_spec.rb) выглядит следующим образом:

require 'rails_helper'

describe 'books/new' do

  it 'displays the book form' do
    book = stub_model(Book)
    assign(:book, book)
    render
    expect(rendered).to have_selector("form label[for *= 'Title']")
    expect(rendered).to have_selector("form label[for *= 'Author']")
    expect(rendered).to have_selector("form label[for *= 'Cover Photo']")
    expect(rendered).to have_button "Add Book"
  end
end

и ошибка следующая:

1) books/new displays the book form
     Failure/Error: book = stub_model(Book)
     NoMethodError:
       undefined method `stub_model' for #<RSpec::ExampleGroups::BooksNew:0x00000103e61870>
     # ./spec/views/books_spec.rb:6:in `block (2 levels) in <top (required)>'

Мой rails_helper.rb выглядит так:

# This file is copied to spec/ when you run 'rails generate rspec:install'
ENV["RAILS_ENV"] ||= 'test'
require 'spec_helper'
require File.expand_path("../../config/environment", __FILE__)
require 'rspec/rails'

# Requires supporting ruby files with custom matchers and macros, etc, in
# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
# run as spec files by default. This means that files in spec/support that end
# in _spec.rb will both be required and run as specs, causing the specs to be
# run twice. It is recommended that you do not name files matching this glob to
# end with _spec.rb. You can configure this pattern with with the --pattern
# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }

# Checks for pending migrations before tests are run.
# If you are not using ActiveRecord, you can remove this line.
ActiveRecord::Migration.maintain_test_schema!

RSpec.configure do |config|
  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
  config.fixture_path = "#{::Rails.root}/spec/fixtures"

  # If you're not using ActiveRecord, or you'd prefer not to run each of your
  # examples within a transaction, remove the following line or assign false
  # instead of true.
  config.use_transactional_fixtures = true

  # RSpec Rails can automatically mix in different behaviours to your tests
  # based on their file location, for example enabling you to call `get` and
  # `post` in specs under `spec/controllers`.
  #
  # You can disable this behaviour by removing the line below, and instead
  # explicitly tag your specs with their type, e.g.:
  #
  #     RSpec.describe UsersController, :type => :controller do
  #       # ...
  #     end
  #
  # The different available types are documented in the features, such as in
  # https://relishapp.com/rspec/rspec-rails/docs
  config.infer_spec_type_from_file_location!
end

и мой Gemfile.rb:

source 'https://rubygems.org'


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.1.2.rc1'
# Use postgresql as the database for Active Record
gem 'pg'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.3'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'
# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer',  platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.0'
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', '~> 0.4.0',          group: :doc

# Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
gem 'spring',        group: :development


group :test do
  gem 'cucumber-rails', :require => false
  gem 'database_cleaner'
end

group :development, :test do
  gem 'rspec-rails'
  gem 'factory_girl_rails'
end
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Use debugger
# gem 'debugger', group: [:development, :test]