@NewTracker
  public TrackerWithProgress newTracker(
      @Element SubscriptionPartition subscriptionPartition, @Restriction OffsetByteRange range) {
    return trackerFactory.apply(backlogReaderFactory.create(subscriptionPartition), range);
  }
@Test
  public void newTrackerCallsFactory() {
    assertSame(tracker, sdf.newTracker(PARTITION, RESTRICTION));
    verify(trackerFactory).apply(backlogReader, RESTRICTION);
  }