<svg xmlns="http://www.w3.org/2000/svg" height="200" width="400" onload="test()">
 <script type="text/javascript">
   function test() {
     document.getElementsByTagNameNS('http://www.w3.org/2000/svg', 'text')[0].firstChild.data = 'PASS';
   }
 </script>
 <text x="20" y="20" font-size="20">FAIL: This text should change.</text>
</svg>