text: // In an ideal world this test would eventually be obsolete due to mutation events disappearing. Or
  // would have to change to account for mutation events not firing synchronously. Neither seems
  // realistic to the author though.
  
  test(t => {
    const frame = document.body.appendChild(document.createElement("iframe"));
    frame.contentWindow.addEventListener("DOMNodeInserted", t.unreached_func());
    frame.contentWindow.addEventListener("DOMNodeInserted", t.unreached_func(), true);
    frame.contentWindow.addEventListener("DOMNodeInsertedIntoDocument", t.unreached_func(), true);
    frame.contentWindow.addEventListener("DOMNodeRemoved", t.unreached_func());
    frame.contentWindow.addEventListener("DOMNodeRemoved", t.unreached_func(), true);
    frame.contentWindow.addEventListener("DOMNodeRemovedFromDocument", t.unreached_func(), true);
    frame.contentWindow.addEventListener("DOMSubtreeModified", t.unreached_func());
    frame.contentWindow.addEventListener("DOMSubtreeModified", t.unreached_func(), true);
    assert_equals(frame.contentDocument.documentElement.localName, "html");
    frame.contentDocument.open();
    assert_equals(frame.contentDocument.documentElement, null);
    frame.contentDocument.write("<div>heya</div>");
    frame.contentDocument.close();
    assert_equals(frame.contentDocument.documentElement.localName, "html");
    frame.remove();
  }, "document.open(), the HTML parser, and mutation events");
  