code: @Test public void should_merge() throws Exception {
    Long userId=RandomUtils.nextLong();
    Long originalAuthorId=RandomUtils.nextLong();
    UUID tweetId=UUIDGen.getTimeUUID();
    Date creationDate=new Date();
    ClusteredTweetId id=new ClusteredTweetId(userId,tweetId,creationDate);
    ClusteredTweetEntity tweet=new ClusteredTweetEntity(id,"this is a tweet",userId,false);
    tweet=manager.persist(tweet);
    tweet.setContent("this is a new tweet2");
    tweet.setIsARetweet(true);
    tweet.setOriginalAuthorId(originalAuthorId);
    manager.update(tweet);
    ClusteredTweetEntity found=manager.find(ClusteredTweetEntity.class,id);
    assertThat(found.getContent()).isEqualTo("this is a new tweet2");
    assertThat(found.getOriginalAuthorId()).isEqualTo(originalAuthorId);
    assertThat(found.getIsARetweet()).isTrue();
  }
  