# File lib/capybara/xpath.rb, line 150
    def add_field(locator, field, options={})
      postfix = extract_postfix(options)
      xpath = append("#{field}[@id=#{s(locator)}]#{postfix}")
      xpath = xpath.append("#{field}[@name=#{s(locator)}]#{postfix}")
      xpath = xpath.append("#{field}[@id=//label[contains(.,#{s(locator)})]/@for]#{postfix}")
      xpath = xpath.append("//label[contains(.,#{s(locator)})]#{field}#{postfix}")
      xpath.prepend("#{field}[@id=//label[text()=#{s(locator)}]/@for]#{postfix}")
    end