In MobileFrontend in browser tests we commonly wait for a ResourceLoader module to be present
This is becoming increasingly useful and should be made to be a global Ruby helper.

Sample code for module name skins.minerva.scripts

on(ArticlePage) do |page|
  page.wait_until do
    browser.execute_script("return mw.loader.getState('skins.minerva.scripts') === 'ready'")
  end
end