<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<base id="base" href="invalid:">
<svg id="svg">
  <pattern id="pat" xlink:href="#pat"/>
</svg>
<script>
  async_test(t => {
    onload = t.step_func_done(() => {
      let pattern = document.getElementById("pat");
      base.href = "";
      document.body.insertBefore(document.getElementById("svg").cloneNode(true),
                                 document.body.firstChild);
      documen