mozilla-release/testing/web-platform/tests/server-timing/service_worker_idl.https.html

<!DOCTYPE html>
<head>
    <meta charset='utf-8' />
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
    <script>
      (async () => {
        const scope = 'does/not/exist'

        let registration = await navigator.serviceWorker.getRegistration(scope)
        if (registration)
          await registration.unregister()
        registration = await navigator.serviceWorker.register('./sw.js', {scope})

        fetch_tests_from_worker(registration.installing)
      })()
    </script>
</head>