ment.createElement('p');
  b1.before(b1_a, 'over 9000');
  testing.expectEqual('<p></p>over 9000<div></div>', before_container.innerHTML);
</script>

<script id=after>
  const after_container = document.createElement('div');
  document.append(after_container);
  const a1 = document.createElement('div');
  after_container.append(a1);

  const a1_a = document.createElement('p');
  a1.after('over 9000', a1_a);
  testing.expectEqual('<div></div>over 9000<p></p>', after_container.innerHTML);
</script>

<script i