<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 -4 100 5" font-size="5">
 <text>FAIL (script didn't run)</text>
 <html xmlns="http://www.w3.org/1999/xhtml">
  <head>
   <script>
    try { // SVGDocument.title is readonly
     document.title = "x";
    } catch (e) {
    }
    var text = document.getElementsByTagName("text")[0];
    text.firstChild.data = document.title == "x" ? "FAIL" : "PASS (as far as HTML is concerned, anyway)";
   </script>
  </head>
 </html>
</svg>
