@Override
  public synchronized String toString() {
    return toStringHelper(ByteKeyRangeTracker.class)
        .add("range", range)
        .add("position", position)
        .toString();
  }
@Test
  public void testToString() {
    ByteKeyRangeTracker tracker = ByteKeyRangeTracker.of(INITIAL_RANGE);
    String expected = String.format("ByteKeyRangeTracker{range=%s, position=null}", INITIAL_RANGE);
    assertEquals(expected, tracker.toString());

    tracker.tryReturnRecordAt(true, INITIAL_START_KEY);
    tracker.tryReturnRecordAt(true, INITIAL_MIDDLE_KEY);
    expected =
        String.format(
            "ByteKeyRangeTracker{range=%s, position=%s}", INITIAL_RANGE, INITIAL_MIDDLE_KEY);
    assertEquals(expected, tracker.toString());
  }