gecko/layout/reftests/css-ui-valid/input/input-fieldset-legend.html

<!DOCTYPE html>
<html>
  <!-- Test: if input has a disabled fieldset ancestor, but is in the first
             legend, it is not barred from constraint validation and should be
             affected by :-moz-ui-valid pseudo-class. -->
  <link rel='stylesheet' type='text/css' href='style.css'>
  <body>
    <fieldset disabled>
      <legend>
        <input class='notvalid'></input>
      </legend>
    </fieldset>
  </body>
</html>