Comment puis-je résoudre Manquant “l'hôte de lien! Veuillez fournir l' :paramètre host”? (RoR)

Je suis à la suite de la RoR Tutoriel et je suis coincé à la Liste 9.15

J'obtiens l'erreur suivante après l'exécution de 'bundle exec rspec spec/' :

1) Authentication authorization as wrong user submitting a PATCH request to the Users#update action 
     Failure/Error: specify { expect(response).to redirect_to(root_url) }
     ArgumentError:
       Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true
     # ./spec/features/authentication_pages_spec.rb:79:in `block (5 levels) in <top (required)>'

Mon test d'Authentification code est:

besoin d'un spec_helper.rb'

describe "Authentication", type: :request do
subject { page }
describe "signin page" do
before { visit signin_path }
it { should have_content('Sign in') }
it { should have_title('Sign in') }
end
describe "signin" do
before { visit signin_path }
describe "with invalid information" do
before { click_button "Sign in" }
it { should have_title('Sign in') }
it { should have_selector('div.alert.alert-error', text: 'Invalid') }
describe "after visiting another page" do
before { click_link "Home" }
it { should_not have_selector('div.alert.alert-error') }
end
end
describe "with valid information" do
let(:user) { FactoryGirl.create(:user) }
before { sign_in user }
#it { should have_title(user.name) }
it { should have_link('Profile',     href: user_path(user)) }
it { should have_link('Settings',    href: edit_user_path(user)) }
it { should have_link('Sign out',    href: signout_path) }
it { should_not have_link('Sign in', href: signin_path) }
describe "followed by signout" do
before { click_link "Sign out" }
it { should have_link('Sign in') }
end
end
end
describe "authorization" do
describe "for non-signed-in users" do
let(:user) { FactoryGirl.create(:user) }
describe "in the Users controller" do
describe "visiting the edit page" do
before { visit edit_user_path(user) }
it { should have_title('Sign in') }
end
describe "submitting to the update action" do
before { patch user_path(user) }
specify { expect(response).to redirect_to(signin_path) }
end
end
end
describe "as wrong user" do
let(:user) { FactoryGirl.create(:user) }
let(:wrong_user) { FactoryGirl.create(:user, email: "[email protected]") }
before { sign_in user, no_capybara: true }
describe "visiting Users#edit page" do
before { visit edit_user_path(wrong_user) }
#it { should_not have_title(full_title('Edit user')) }
end
describe "submitting a PATCH request to the Users#update action" do
before { patch user_path(wrong_user) }
specify { expect(response).to redirect_to(root_url) }
end
end
end
end

Je ne sais pas comment résoudre ce problème de sorte que le test passe. Comment ne - je le résoudre? Quelqu'un pourrait-il expliquer ce qui ne va pas? (D'après le tutoriel, le test doit être de passage).