Rails tutorial ６章エラー

Question

rails tutorialの６章をやっているのですがrails testを行うと

Error:
UsersControllerTest#test_should_get_new:
NoMethodError: undefined method `each' for nil:NilClass

StaticPagesControllerTest#test_should_get_about:
NoMethodError: undefined method `each' for nil:NilClass

という二つのエラーが出てしまいます。
どの様に解決すればよいでしょうか？

require 'test_helper'

class UsersControllerTest < ActionDispatch::IntegrationTest
  test "should get new" do
    get signup_path
    assert_response :success
  end

end

require 'test_helper'
class StaticPagesControllerTest < ActionDispatch::IntegrationTest
  def setup
    @base_title= "Ruby on Rails Tutorial Sample App"
  end
  test "should get home" do
    get root_path
    assert_response :success
    assert_select "title", "Ruby on Rails Tutorial Sample App"
  end

  test "should get help" do
    get help_path 
    assert_response :success
    assert_select "title", "Help | #{@base_title}"
  end
  test "should get about" do
    get about_path
    assert_response :success
    assert_select "title", "About | #{@base_title}"
  end
  test "should get contact" do
    get contact_path
    assert_response :success
    assert_select "title", "Contact | #{@base_title}"
  end

end