@VisibleForTesting
  @SuppressWarnings("unchecked")
  TimelineDoc applyUpdatesOnPrevDoc(CollectionType collectionType,
      TimelineDoc timelineDoc, StringBuilder eTagStrBuilder) {
    TimelineDoc prevDocument = fetchLatestDoc(collectionType,
        timelineDoc.getId(), eTagStrBuilder);
    if (prevDocument != null) {
      prevDocument.merge(timelineDoc);
      timelineDoc = prevDocument;
    }
    return timelineDoc;
  }
@SuppressWarnings("unchecked")
  @Test
  public void applyingUpdatesOnPrevDocTest() throws IOException {
    MockedCosmosDBDocumentStoreWriter documentStoreWriter =
        new MockedCosmosDBDocumentStoreWriter(null);

    TimelineEntityDocument actualEntityDoc =
        new TimelineEntityDocument();
    TimelineEntityDocument expectedEntityDoc =
        DocumentStoreTestUtils.bakeTimelineEntityDoc();

    Assert.assertEquals(1, actualEntityDoc.getInfo().size());
    Assert.assertEquals(0, actualEntityDoc.getMetrics().size());
    Assert.assertEquals(0, actualEntityDoc.getEvents().size());
    Assert.assertEquals(0, actualEntityDoc.getConfigs().size());
    Assert.assertEquals(0,
        actualEntityDoc.getIsRelatedToEntities().size());
    Assert.assertEquals(0, actualEntityDoc.
        getRelatesToEntities().size());

    actualEntityDoc = (TimelineEntityDocument) documentStoreWriter
        .applyUpdatesOnPrevDoc(CollectionType.ENTITY,
            actualEntityDoc, null);

    Assert.assertEquals(expectedEntityDoc.getInfo().size(),
        actualEntityDoc.getInfo().size());
    Assert.assertEquals(expectedEntityDoc.getMetrics().size(),
        actualEntityDoc.getMetrics().size());
    Assert.assertEquals(expectedEntityDoc.getEvents().size(),
        actualEntityDoc.getEvents().size());
    Assert.assertEquals(expectedEntityDoc.getConfigs().size(),
        actualEntityDoc.getConfigs().size());
    Assert.assertEquals(expectedEntityDoc.getRelatesToEntities().size(),
        actualEntityDoc.getIsRelatedToEntities().size());
    Assert.assertEquals(expectedEntityDoc.getRelatesToEntities().size(),
        actualEntityDoc.getRelatesToEntities().size());
  }