dom/nodes/Node-cloneNode-XMLDocument.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Cloning of an XMLDocument</title>
<link rel="help" href="https://dom.spec.whatwg.org/#dom-node-clonenode">
<link rel="help" href="https://dom.spec.whatwg.org/#concept-node-clone">

<!-- This is testing in particular "that implements the same interfaces as node" -->

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<script>
"use strict";

test(() => {
  const doc = document.implementation.createDocument("namespace", "");

  assert_equals(
    doc.constructor, XMLDocument,
    "Precondition check: document.implementation.createDocument() creates an XMLDocument"
  );

  const clone = doc.cloneNode(true);

  assert_equals(clone.constructor, XMLDocument);
}, "Created with createDocument");

</script>