css/css-scoping/font-face-006.html

<!doctype html>
<title>CSS Test: @font-face from document applies to :host::before/::after.</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="author" title="Alan Stearns" href="mailto:stearns@adobe.com">
<link rel="help" href="https://drafts.csswg.org/css-scoping/#shadow-names">

<style>
@font-face {
  font-family: ff-16-wide;
  src: url(/fonts/Ahem.ttf);
}
#host {
  float: left;
}
</style>
<div id="host"></div>
<script>
promise_test(async () => {
  host.attachShadow({ mode: "open" }).innerHTML = `
    <style>
      :host::before, :host::after {
        font-family: ff-16-wide;
        content: "12345"
      }
    </style>
    <slot></slot>
  `;

  await document.fonts.ready;

  //shrinkwrapped size for a default font will be a bit more than 80-90
  //if the font is applied, it will be a bit more than 160
  assert_greater_than(document.getElementById('host').offsetWidth, 160);
}, "@font-face from document applies to to :host::before/::after.");
</script>