How can I change the phantomjs viewportSize?

[Josué Henrique Ferreira da Silva]

I find somthing like it

Capybara.register_driver :poltergeist do |app|
  options = {
    #The dimensions of the browser window in which to test, expressed as a 2-element array,
    :window_size => [1280, 800],
    :js_errors => false
  }