return formatDate(Date(System.currentTimeMillis() + timeUnit.toMillis(delta)))
  }

  private fun formatDate(date: Date): String {
    val rfc1123: DateFormat = SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US)
    rfc1123.timeZone = TimeZone.getTimeZone("GMT")
    return rfc1123.format(date)
  }

  private fun assertNotCached(response: MockResponse) {
    server.enqueue(
      response.newBuilder()