void update(int indexToChange) {
    update(indexToChange, null);
  }
@Test
  public void update() {
    helper.update(1); // New Batch
    helper.update(0); // Update at start of batch
    helper.update(2); // Update at end of batch
    helper.update(0); // Update same item as before (shouldn't be added to batch length)

    List<UpdateOp> opList = helper.opList;
    assertEquals(1, opList.size());

    assertEquals(0, opList.get(0).positionStart);
    assertEquals(3, opList.get(0).itemCount);

    assertEquals(0, helper.getNumInsertionBatches());
    assertEquals(0, helper.getNumInsertions());
    assertEquals(0, helper.getNumRemovalBatches());
    assertEquals(0, helper.getNumRemovals());
    assertEquals(0, helper.getNumMoves());
  }