firefox/testing/web-platform/tests/css/css-backgrounds/reference/reference.html

<!DOCTYPE html>
<html>
  <head>

    <title>CSS Background and Borders Test:background-clip_pending-box</title>
    <link rel="author" title="anping" href="mailto:[email protected]" />
    <meta content="Check if the border-clip works.">
    <style>
      div{
          position:absolute;
         }

       #outside{

        border: blue dotted 5px;
        height: 120px;
        left: 10px;
        top: 10px;
        width: 120px;
        background-color:transparent;

       }
      #inside{

        border: transparent;
        height: 100px;
        left: 25px;
        top: 25px;
        width: 100px;
        background-color:red;

       }

    </style>
  </head>
 <body>
  <p>
   "Test passes if the border is blue dotted without red."
  </p>
  <div id="container">

   <div id="outside"></div>
   <div id="inside"></div>
  </div>
 </body>

</html>