rspecによるdeviseを用いた新規登録画面のcontrollerの単体テストの際のエラー（undefined method `validatable?' for nil:NilClass）

Question

前提・実現したいこと

Ruby on rails を用いてdeviseを用いた新規登録機能を実装
newアクションで新規登録画面に遷移し、new.html.hamlが表示されるかのcontrollerの単体テストを行おうとしたが、
以下のエラーメッセージ(NoMethodError:undefined method `validatable?' for nil:NilClass)が発生しました。
ググってみたのですが解決できず、初心者で基本的なことかもしれず申し訳ないのですが、ご教授いただければと思います。

発生している問題・エラーメッセージ

Users::RegistrationsController
  GET #new
    renders the :new template (FAILED - 1)

Failures:

  1) Users::RegistrationsController GET #new renders the :new template
     Failure/Error: get :new
     
     NoMethodError:
       undefined method `validatable?' for nil:NilClass
     # ./spec/controllers/users/registrations_controller_spec.rb:7:in `block (3 levels) in <top (required)>'

Finished in 0.01058 seconds (files took 4.25 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/controllers/users/registrations_controller_spec.rb:6 # Users::RegistrationsController GET #new renders the :new template

該当のソースコード

spec/controllers/users/registrations_controller_spec.rb

require 'rails_helper'

describe Users::RegistrationsController, type: :controller  do

  describe 'GET #new' do
    it "renders the :new template" do
      get :new
      expect(response).to render_template :new
    end
  end
end

app/controller/users/registrations_controller.rb

# frozen_string_literal: true

class Users::RegistrationsController < Devise::RegistrationsController
  before_action :configure_sign_up_params, only: [:create]
  # before_action :configure_account_update_params, only: [:update]

  # GET /resource/sign_up

  def new
    @user = User.new
  end

  # POST /resource
  def create
    @user = User.new(sign_up_params)
    unless @user.valid?
      flash.now[:alert] = @user.errors.full_messages
      render :new and return
    end
    session["devise.regist_data"] = {user: @user.attributes}
    session["devise.regist_data"][:user]["password"] = params[:user][:password]
    @cellphone = @user.build_cellphone
    render :new_cellphone
  end

  def create_cellphone
    @user = User.new(session["devise.regist_data"]["user"])
    @cellphone = Cellphone.new(cellphone_params)
    unless @cellphone.valid?
      flash.now[:alert] = @cellphone.errors.full_messages
      render :new_cellphone and return
    end
    @user.build_cellphone(@cellphone.attributes)
    session["cellphone"] = @cellphone.attributes
    @address = @user.build_address
    render :new_address
  end

  def create_address
    @user = User.new(session["devise.regist_data"]["user"])
    @cellphone = Cellphone.new(session["cellphone"])
    @address = Address.new(address_params)
    unless @address.valid?
      flash.now[:alert] = @address.errors.full_messages
      render :new_address and return
    end
    @user.build_cellphone(@cellphone.attributes)
    @user.build_address(@address.attributes)
    session["address"] = @address.attributes
    @card = @user.build_card
    render :new_card
  end


  def create_card
    @user = User.new(session["devise.regist_data"]["user"])
    @cellphone = Cellphone.new(session["cellphone"])
    @address = Address.new(session["address"])
    @card = Card.new(card_params)
    unless @card.valid?
      flash.now[:alert] = @card.errors.full_messages
      render :new_card and return
    end
    @user.build_cellphone(@cellphone.attributes)
    @user.build_address(@address.attributes)
    @user.build_card(@card.attributes)
    @user.save
    sign_in(:user, @user)
  end 

  # GET /resource/edit
  # def edit
  #   super
  # end

  # PUT /resource
  # def update
  #   super
  # end

  # DELETE /resource
  # def destroy
  #   super
  # end

  # GET /resource/cancel
  # Forces the session data which is usually expired after sign
  # in to be expired now. This is useful if the user wants to
  # cancel oauth signing in/up in the middle of the process,
  # removing all OAuth session data.
  # def cancel
  #   super
  # end

  protected

  # If you have extra params to permit, append them to the sanitizer.
  def configure_sign_up_params
    devise_parameter_sanitizer.permit(:sign_up, keys: [:attribute])
  end

  def cellphone_params
    params.require(:cellphone).permit(:number)
  end

  def address_params
    params.require(:address).permit(:zip_code, :prefecture, :city, :address, :building, :phone_tell)
  end

  def card_params
    params.require(:card).permit(:number, :validated_date_year, :validated_date_month, :security_number)
  end



  # If you have extra params to permit, append them to the sanitizer.
  # def configure_account_update_params
  #   devise_parameter_sanitizer.permit(:account_update, keys: [:attribute])
  # end

  # The path used after sign up.
  # def after_sign_up_path_for(resource)
  #   super(resource)
  # end

  # The path used after sign up for inactive accounts.
  # def after_inactive_sign_up_path_for(resource)
  #   super(resource)
  # end
end

spec/rails_helper.rb

# This file is copied to spec/ when you run 'rails generate rspec:install'
require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'

require File.expand_path('../config/environment', __dir__)

# Prevent database truncation if the environment is production
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'rspec/rails'
# Add additional requires below this line. Rails is not loaded until this point!

# 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 the --pattern
# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
#
# The following line is provided for convenience purposes. It has the downside
# of increasing the boot-up time by auto-requiring all files in the support
# directory. Alternatively, in the individual `*_spec.rb` files, manually
# require only the support files necessary.
#
# Dir[Rails.root.join('spec', 'support', '**', '*.rb')].each { |f| require f }

# Checks for pending migrations and applies them before tests are run.
# If you are not using ActiveRecord, you can remove these lines.
begin
  ActiveRecord::Migration.maintain_test_schema!
rescue ActiveRecord::PendingMigrationError => e
  puts e.to_s.strip
  exit 1
end
RSpec.configure do |config|
  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
  config.fixture_path = "#{::Rails.root}/spec/fixtures"
  config.include FactoryBot::Syntax::Methods
  # 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!

  # Filter lines from Rails gems in backtraces.
  config.filter_rails_from_backtrace!
  # arbitrary gems may also be filtered via:
  # config.filter_gems_from_backtrace("gem name")
end

config/routes.rb

Rails.application.routes.draw do
  devise_for :users, controllers: {
    registrations: 'users/registrations',
  }
  devise_scope :user do
    get 'cellphones', to: 'users/registrations#new_cellphone'
    post 'cellphones', to: 'users/registrations#create_cellphone'
    get 'addresses', to: 'users/registrations#new_address'
    post 'addresses', to: 'users/registrations#create_address'
    get 'cards', to: 'users/registrations#new_card'
    post 'cards', to: 'users/registrations#create_card'
  end
  root to: "items#index"
  resources :items
  resources :credit_cards, only: [:index,:new,:show]
end

補足情報（FW/ツールのバージョンなど）

ruby '2.5.1'
'rails', '~> 5.2.3'

Answer 1

deviseのテストコードですが参考になると思います。
test/controllers/custom_registrations_controller_test.rb

Comments

[shuya-tamaru]

参考資料を元に

@request.env["devise.mapping"] = Devise.mappings[:user]
の追加と
rails_helper.rb
に
config.include Devise::Test::ControllerHelpers, type: :controllerを追加したらerror消えました！
要因は今から調べてみようと思います！
ありがとうございます！