Test "dynamic" page title in a view spec (Rails 4 + RSpec 3)

I am currently following a tutorial but Rails and Rspec have evolved, especially for writing tests.

My goal is to test that when I visit the page "http://domain.fr/users/1" the page title follow the format : "#{base_title} | #{@user.name}" where base_title is constant.

Before, I saw it was possible to use render_views in controller specs but it is not the best way and it does not exist anymore in Rails 4/RSpec 3.

My last try is :

require 'rails_helper'

describe "users/show.html.erb", type: :view do

    it "Shoud finally render a correct title" do

        user = FactoryGirl.create(:user)
        assign(:user, user)
        render template: "users/show.html.erb", layout: "layouts/application.html.erb"
        expect(rendered).to have_selector("title", text: user.name)
    end
end

I use an helper for rendering in application.html.erb : <title><%= title %></title>

Here is the helper :

def title
    base_title = "Simple App du Tutoriel Ruby on Rails"
    @title.nil? ? base_title : "#{base_title} | #{@title}"
end

And the show method from users_controller.rb :

def show
    @user = User.find(params[:id])
    @title = @user.name
end

I also added resources :users to my routes.rb file.

For FactoryGirl here is user.rb :

FactoryGirl.define do
    factory :user do
        name "Antoine Foucault"
        email "a@b.c"
        password "password"
        password_validation "password"
    end
end

The above test fail because only the constant part of the title is rendered. Thus, I think Users#show is not called and @title not defined but I don't see how to achieve this.

Thanks for your help :)