  @Test
  public void testCardinality() {

    SplitMapPageWriter writer = new SplitMapPageWriter();
    writer.add(1);
    writer.add(1 << 14);
    writer.add(1 << 16 | 1);
    writer.add(1 << 17);
    assertEquals(writer.toSplitMap().getCardinality(), 4);
  }