uerySelector('rt').getBoundingClientRect();
  document.querySelector('ruby').style.left = '100px';
  const rtAfter = document.querySelector('rt').getBoundingClientRect();
  assert_equals(rtBefore.x + 100, rtAfter.x);
}, 'position:relative on a ruby should move the annotation together');

test(() => {
  container.innerHTML = `<span style="position:relative">
      <ruby>base<rt>annotation</ruby></span>`;
  const rubyBefore = document.querySelector('ruby').getBoundingClientRect();
  const rtBefore = document.