chromium/third_party/blink/web_tests/external/wpt/resource-timing/resource-timing-failed-fetch.html

<!doctype html>

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="stylesheet" href="resources/empty_style.css">
<link rel="stylesheet" href="resources/non_exist.css">

<script>
  promise_test(async () => {
    const css_resource_timing_entries = await new Promise(resolve => {
      new PerformanceObserver((list, observer) => {
        let css_resource_timing_entries = list.getEntries().filter(e => e.name.includes('css'));
        if (css_resource_timing_entries.length >= 2) {
          resolve(css_resource_timing_entries);
        }
      }).observe({ 'type': 'resource', 'buffered': true });
    });

    assert_equals(css_resource_timing_entries.length, 2,
      'There should be two resource timing entries for css resources');

    assert_equals(css_resource_timing_entries.filter(
      e => e.name.includes('empty_style.css')).length, 1,
      'There should be one resource timing entry for successfully fetched resource.');

    assert_equals(css_resource_timing_entries.filter(
      e => e.name.includes('non_exist.css')).length, 1,
      'There should be one resource timing entry for fetching failed resource.');

  }, 'Resource fetched by HTTP protocol should have resource timing entry emitted, \
  even when the fetch failed.');
</script>

</html>