chromium/third_party/blink/web_tests/editing/pasteboard/paste-xml.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" 
   "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>

<div contenteditable="" id="root">
<span id="test">foo bar baz</span>
</div>

<script>
test(() => {
  assert_not_equals(window.internals, undefined,
                    'This test requires clipboard access');

  const selection = window.getSelection();
  const root = document.getElementById('root');
  const test = document.getElementById('test');

  selection.setBaseAndExtent(test.firstChild, 4, test.firstChild, 7); // foo ^bar| baz
  document.execCommand('copy');
  selection.collapse(test.firstChild, 7); // foo bar| baz
  document.execCommand('paste');

  const expectedText = '\n&lt;span xmlns=\"http://www.w3.org/1999/xhtml\" id=\"test\"&gt;foo barbar baz&lt;/span&gt;\n';
  assert_equals(root.innerHTML, expectedText);
  assert_equals(selection.anchorNode, test.firstChild);
  assert_equals(selection.anchorOffset, 10);
  assert_equals(selection.type, 'Caret');
}, 'Paste in XML');
</script>

</html>