<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-transitions/#starting">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  div { height: inherit; }
  #outer { height: 50px; }
  #outer.collapsed {
    height: 0px;
    transition: height 0.01s;
  }
</style>
<div id="outer">
  <div>
    <div id="inner">You should only see a flash of red.</div>
  </div>
</div>
<script>
  promise_test(t => {
    outer.offsetTop;
    outer.classN