third_party/web_platform_tests/dom/nodes/Node-baseURI.html

<!DOCTYPE html>
<title>Node.baseURI</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="log"></div>
<script>
test(function() {
  var element = document.createElement("div");
  document.body.appendChild(element);
  assert_equals(element.baseURI, document.URL);
}, "For elements belonging to document, baseURI should be document url")

test(function() {
  var element = document.createElement("div");
  assert_equals(element.baseURI, document.URL);
}, "For elements unassigned to document, baseURI should be document url")

test(function() {
  var fragment = document.createDocumentFragment();
  var element = document.createElement("div");
  fragment.appendChild(element);
  assert_equals(element.baseURI, document.URL)
}, "For elements belonging to document fragments, baseURI should be document url")

test(function() {
  var fragment = document.createDocumentFragment();
  var element = document.createElement("div");
  fragment.appendChild(element);
  document.body.appendChild(fragment);
  assert_equals(element.baseURI, document.URL)
}, "After inserting fragment into document, element baseURI should be document url")
</script>