chromium/third_party/blink/web_tests/fast/dom/comment-document-fragment.html

<!-- this comment should show up as the
     first child of the HTML element in the DOM.
     the document should also say "SUCCESS",
     if you don't see SUCCESS then the DOM was
     not built correctly because of this comment -->
<script>
if (window.testRunner)
    testRunner.dumpAsText();
</script>
SUCCESS