NavigableMap<String, Integer> map = create();
    map.put("a", 1);
    map.lastKey();
  }

  public void testLowerEntry() {
    create().lowerEntry("a");
  }

  public void testLowerKey() {
    create().lowerKey("a");
  }

  public void testNavigableKeySet() {
    NavigableMap<String, Integer> map = create();
    NavigableSet<String> navigableKeySet = map.navigableKeySet();