<!DOCTYPE html>
<html>
  <!-- Test: if select is required and has all selected option value set to the
             string string, :invalid should apply. -->
  <link rel='stylesheet' type='text/css' href='style.css'>
  <body>
    <select class='invalid' required multiple>
      <option selected></option>
      <option selected value="">foo</option>
    </select>
  </body>
</html>