assertNull(subMap.remove(firstEntry.getKey()));
    assertEquals(map.size(), oldSize - 1);
    assertFalse(map.containsKey(key));
    assertEquals(subMap.size(), oldSize - 2);
  }

  public void testTailMapClearThrough() {
    SortedMap<K, V> map;
    try {
      map = makePopulatedMap();
    } catch (UnsupportedOperationException e) {
      return;
    }
    int oldSize = map.size();