Testing Rails: defining temporary controller, view and route in feature spec

index.html.erb

<% # This file lives at spec/features/views/index.html.erb %>
<h1>My Temporary Page</h1>

temporary_controller_view_route_spec.rb

feature 'add temporary controller, view, and route for testing', :js do
  before do
    klass = Class.new(ApplicationController) do
      prepend_view_path 'spec/features/views'

      def index
        # Put an index.html.erb file in spec/features/views
        render template: 'index'
      end
    end
    stub_const('TemporaryController', klass)

    Rails.application.routes.disable_clear_and_finalize = true # preserve original routes
    Rails.application.routes.draw do
      get '/temp-path', to: 'temporary#index'
    end
  end

  # Reset routes so they don't include test mapping from above.
  after { Rails.application.reload_routes! }

  scenario 'view temporary page' do
    visit '/temp-path'
    expect(page).to have_css 'h1', text: 'My Temporary Page'
  end
end