Rails system test that:Creates new facebook test user with koala gem. Signs in user on facebook.com. Accepts facebook "continue as #{username}" iframe.

facebook_login_capybara_koala_minitest.rb

# frozen_string_literal: true

require 'application_system_test_case'

class FacebookLoginTest < ApplicationSystemTestCase
  
  # create new test user with Koala Gem
  def setup
    @test_users = Koala::Facebook::TestUsers.new
    @user = @test_users.create(false)

    login_in_facebook(@user)
  end

  def teardown
    @test_users.delete(@user)
  end

  def test_login_with_facebook
    visit spa_page_with_facebook_login_url

    # on your app click on the "Login with facebook" button
    facebook_login_window = window_opened_by do
      click_on 'Login with facebook'
    end

    # click on "continue as USERNAME" on the facebook iframe
    within_window(facebook_login_window) do
      find(:xpath, "//button[contains(@name, '__CONFIRM__')]").click
    end
  end

  private

  # Logs in test user on facebook.com
  def login_in_facebook(user)
    Capybara.always_include_port = false

    visit 'https://www.facebook.com'

    fill_in :email, with: user['email']
    fill_in :pass, with: user['password']

    find('#loginbutton').click

    Capybara.always_include_port = true
  end
end