@Test public void flagIsSetShouldReturnUidOfMessageMarkedAsSeenWhenUsedWithFlagSeen() throws MailboxException {
  SearchQuery searchQuery=new SearchQuery();
  searchQuery.andCriteria(SearchQuery.flagIsSet(Flags.Flag.SEEN));
  assertThat(elasticSearchListeningMessageSearchIndex.search(session,mailbox,searchQuery)).containsOnly(6L);
}