browser_size.rb

#backend/spec/support/browser_size.rb

# note, our Rails app is not in the repo root.  We have: 
# <root>/backend      (Rails back-end app)
# <root>/frontend     (AngularJS front-end SPA)

module BrowserSize
  SIZES = {
    :mobile  => { :width => 320, :height => 480 },
    :small   => { :width => 550, :height => 700 },
    :medium  => { :width => 800, :height => 900 },
    :desktop => { :width => 1024, :height => 1024 }
  }

  RSpec.configure do |config|
    config.before(:each) do
      if RSpec.current_example.metadata[:js]
        BrowserSize.resize_browser_window(SIZES[BrowserSize.current_size])
      end
    end
  end

  def self.resize_browser_window(size)
    Capybara.current_session.driver.browser.manage.window.resize_to(size[:width], size[:height])
  end

  def self.current_size
    (RSpec.current_example.metadata[:size] || ENV['BROWSER_SIZE'] || :desktop).to_sym
  end

end

RSpec.configure do |config|
  config.include BrowserSize, :type => :feature
end

Rakefile

namespace :spec do
   
  # ... other stuff ...
  
  desc "Run all feature specs, repeating with each browser width as default"
  task :responsivity, [:spec_files] => [:links, 'backend:setup'] do |t, args|
    Bundler.with_clean_env do
      %w{mobile small medium desktop}.each do |size|
        Dir.chdir("backend"){
          ENV['BROWSER_SIZE']=size
          commands = ["bundle", "exec", "rspec", "-o", "tmp/rspec_#{size}.txt"]
          if args[:spec_files]
            commands.push(args[:spec_files])
          else
            commands.push('spec/features')
          end
          sh *commands rescue true
        }
      end
    end
  end
end

session_helpers.rb

#backend/spec/support/session_helpers.rb

module Features
  module SessionHelpers
    COLLAPSED_MENU_SIZES=[ :mobile, :small ]

    def visit_login
      visit '/'
      expand_menu_if_necessary
      within ".session-links" do
        click_link "Sign In"
      end
    end

    def expand_menu_if_necessary
      # On pages with collapsed menu, click to expand the menu
      # before trying to click the sign-in link.  I'm doing it this
      # way instead of inspecting the page for .session-links because
      # the latter triggers a capybara wait, which is much slower.
      if COLLAPSED_MENU_SIZES.include?(BrowserSize.current_size)
        click_on('Menu')
      end
    end

    def sign_up_with(email, password)
      visit '/'
      expand_menu_if_necessary
      click_on "Sign Up"
      fill_in "Email",           :with => email
      fill_in "Email Confirmation", :with => email
      fill_in "Password",        :with => password
      fill_in "Password Confirmation", :with => password
      click_button "Sign Up"
    end

    def sign_in_with(email, password)
      visit_login
      fill_in "Email", :with => email
      fill_in "Password", :with => password
      click_button "Sign In"
    end
  end
end

visitor_navigates_the_menu_spec.rb

require 'spec_helper'

feature "Visitor navigates with the main menu", :js => true, :vcr => {} do

  let :page_one do
    FactoryGirl.create(:one_column_page)
  end

  let :page_two do
    FactoryGirl.create(:two_column_page)
  end

  let! :page_link do
    FactoryGirl.create(:menu_item, name: 'Page Link', page: page_one)
  end

  let! :path_link do
    FactoryGirl.create(:menu_item_without_page, name: "Path Link", path: '/#/sign-in')
  end

  context "on a desktop", :size => :desktop do
    scenario "visit a path" do
      visit '/'
      click_on("Path Link")
      expect(page).to have_content("Sign In")
      expect(URI(current_url).fragment).to eq('/sign-in')
    end

    scenario "visit a page" do
      visit '/'
      click_on("Page Link")
      expect(page).to have_content(page_one.contents["headline"].body)
      expect(page.body).to include(page_one.contents["main"].body)
      expect(URI(current_url).fragment).to eq("/pages/" + page_one.url_slug)
    end
  end

  context "on a mobile device", :size => :mobile do
    scenario "visit a path" do
      visit '/'
      click_on("Menu")  # Expand the currently-collapsed menu
      click_on("Path Link")
      expect(page).to have_content("Sign In")
      expect(URI(current_url).fragment).to eq('/sign-in')
    end
  end
end