css/css-layout-api/at-supports-rule.https.html

<!DOCTYPE html>
<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#valdef-display-layout">
<meta name="assert" content="This test checks that a layout() function works correctly with an @supports rule." />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#test {
  content: 'fail';
}

@supports (display: layout(foo)) {
  #test {
    content: 'pass';
  }
}
</style>
<div id="test"></div>
<script>
test(function() {
  const element = document.getElementById('test');
  assert_equals(getComputedStyle(element).content, '"pass"');
});
</script>