@Test
public void testCeilingEntry() {

    IncrementalSortMap<Integer, String> map = map5();
    Map.Entry e1 = map.ceilingEntry(three);
    assertEquals(three, e1.getKey());
    Map.Entry e2 = map.ceilingEntry(zero);
    assertEquals(one, e2.getKey());
    Map.Entry e3 = map.ceilingEntry(five);
    assertEquals(five, e3.getKey());
    Map.Entry e4 = map.ceilingEntry(six);
    assertNull(e4);
}