e>
div {
  background: blue;
  color: white;
}
.hidden {
  content-visibility: hidden;
}
</style>

<div>Test passes if the word “FAIL” does not appear below and if there is no red.</div>
<iframe id="frame" width=400 height=200 srcdoc='
  <style>
  div {
    background: red;
  }
  </style>
  <div>FAIL</div>
'></iframe>
<div>Test passes if the word “FAIL” does not appear above and if there is no red.</div>

<script>
async function runTest() {
  document.getElementById("frame").classList.add("hidden");