firefox/devtools/client/storage/test/storage-cache-basic-iframe.html

<!DOCTYPE HTML>
<html>
<head>
  <meta charset="utf-8">
  <title>Storage inspector test for Cache</title>
</head>
<body>
  <h1>Cache (iframe)</h1>
<script>
  "use strict";
  async function setup() { // eslint-disable-line no-unused-vars
    const cache = await caches.open("foo");
    await cache.add("storage-blank.html");
  }
  function clear() { // eslint-disable-line no-unused-vars
    return caches.delete("foo");
  }
</script>

</body>
</html>