Set browser screen size in rspec + capybara suite for responsive web design test.

device_size.rb

# spec/support/device_size.rb

module DeviceSize

  extend ScreenSize

  RSpec.configure do |config|
    config.before(:each) do
      if example.metadata[:device_size].blank?
        # set screen size default to :large
        DeviceSize.set_screen_size DeviceSize.default_size
      else
        DeviceSize.set_screen_size example.metadata[:devise_size]
      end
    end

    # include screen size into feature spec
    config.include ScreenSize, :type => :feature

  end
end