class ActionDispatch::Cookies::CookieJar

def deleted?(name, options = {})

deletion applies to a specific :path, :domain etc.
Like []=, you can pass in an options hash to test if a
Whether the given cookie is to be deleted by this CookieJar. 
def deleted?(name, options = {})
  options.symbolize_keys!
  handle_options(options)
  @delete_cookies[name.to_s] == options
end