@Test
public void shouldUseExistingTimestampHeaderInTimestampedEvent() {

  SimpleEvent base = new SimpleEvent();
  Map<String, String> headersWithTimestamp = Maps.newHashMap();
  headersWithTimestamp.put("timestamp", "-321");
  base.setHeaders(headersWithTimestamp );
  TimestampedEvent timestampedEvent = new TimestampedEvent(base);
  assertEquals(-321L, timestampedEvent.getTimestamp());
  assertEquals("-321", timestampedEvent.getHeaders().get("timestamp"));
}