@Override
  public Date getStartedAt() {
    String dateString = settings.get(CoreProperties.SERVER_STARTTIME).orElseThrow(() -> new IllegalStateException("Mandatory"));
    return DateUtils.parseDateTime(dateString);
  }
@Test(expected = RuntimeException.class)
  public void invalid_startup_date_throws_exception() {
    MapSettings settings = new MapSettings();
    settings.setProperty(CoreProperties.SERVER_STARTTIME, "invalid");
    DefaultScannerWsClient client = mock(DefaultScannerWsClient.class);
    DefaultServer metadata = new DefaultServer(settings.asConfig(), client, null);
    metadata.getStartedAt();
  }