assertEquals(map.headMap("three", true), map.descendingMap().tailMap("three", true));
    assertThat(map.tailMap("three", false).entrySet()).contains(mapEntry("two", 3));
    assertThat(map.tailMap("three", true).lowerEntry("three")).isNull();
    assertThat(map.headMap("two", false).values()).containsExactly(3, 5).inOrder();
    assertThat(map.headMap("two", false).descendingMap().values()).containsExactly(5, 3).inOrder();

  }

  <K, V> void testNavigationAgainstExpected(
      NavigableMap<K, V> expected, NavigableMap<K, V> navigableMap, Iterable<K> keysToTest) {
    for (K key : keysToTest) {
      assertEquals(expected.lowerEntry(key), navigableMap.lowerEntry(key));
      assertEquals(expected.floorEntry(key), navigableMap.floorEntry(key));
      assertEquals(expected.ceilingEntry(key), navigableMap.ceilingEntry(key));