chromium/third_party/blink/web_tests/external/wpt/svg/animations/switching-animated-target-to-unknown-element.html

<!DOCTYPE html>
<title>Switching animated target to an unknown element</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<svg height="0">
  <path id="path">
    <animateMotion/>
  </path>
  <unknown id="unknown"></unknown>
</svg>
<script>
  async_test(t => {
    let path = document.getElementById("path");
    let anim = path.firstElementChild;
    t.step_timeout(() => {
      path.appendChild(document.createElementNS('http://www.w3.org/2000/svg', 'animateMotion'));
      anim.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href', '#unknown');
      requestAnimationFrame(t.step_func(() => {
        requestAnimationFrame(t.step_func_done());
      }));
    });
  });
</script>