@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);
}