public void testCeiling() {
    resetWithHole();
    assertEquals(a, navigableMap.ceilingEntry(a.getKey()));
    assertEquals(a.getKey(), navigableMap.ceilingKey(a.getKey()));
    assertEquals(c, navigableMap.ceilingEntry(b.getKey()));
    assertEquals(c.getKey(), navigableMap.ceilingKey(b.getKey()));
    assertEquals(c, navigableMap.ceilingEntry(c.getKey()));
    assertEquals(c.getKey(), navigableMap.ceilingKey(c.getKey()));
  }

    protected NavigableMap<K, V> delegate() {
      return (NavigableMap<K, V>) super.delegate();
    }

    @Override
    public @Nullable Entry<K, V> ceilingEntry(K key) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().ceilingEntry(key);
    }

    @Override
    public @Nullable K ceilingKey(K key) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate().ceilingKey(key);

    if (delegate == null) {
      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override
  public @Nullable K ceilingKey(K key) {
    return delegate.ceilingKey(checkValid(key));
  }

  @Override
  public void clear() {

    if (delegate == null) {
      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override
  public @Nullable K ceilingKey(K key) {
    return delegate.ceilingKey(checkValid(key));
  }

  @Override
  public void clear() {

    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));
      assertEquals(expected.higherEntry(key), navigableMap.higherEntry(key));
      for (boolean inclusive : new boolean[] {false, true}) {

      super(fromMap, transformer);
    }

    @Override
    @CheckForNull
    public Entry<K, V2> ceilingEntry(@ParametricNullness K key) {
      return transformEntry(fromMap().ceilingEntry(key));
    }

    @Override
    @CheckForNull
    public K ceilingKey(@ParametricNullness K key) {
      return fromMap().ceilingKey(key);
    }

      super(fromMap, transformer);
    }

    @Override
    @CheckForNull
    public Entry<K, V2> ceilingEntry(@ParametricNullness K key) {
      return transformEntry(fromMap().ceilingEntry(key));
    }

    @Override
    @CheckForNull
    public K ceilingKey(@ParametricNullness K key) {
      return fromMap().ceilingKey(key);
    }

    return keyOrNull(floorEntry(key));
  }

  @Override
  @CheckForNull
  public Entry<K, V> ceilingEntry(K key) {
    return tailMap(key, true).firstEntry();
  }

  @Override
  @CheckForNull
  public K ceilingKey(K key) {
    return keyOrNull(ceilingEntry(key));
  }

  @Override
  @CheckForNull
  public Entry<K, V> higherEntry(K key) {

      return (NavigableMap<K, V>) super.delegate();
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> ceilingEntry(K key) {
      synchronized (mutex) {
        return nullableSynchronizedEntry(delegate().ceilingEntry(key), mutex);
      }
    }

    @Override
    @CheckForNull
    public K ceilingKey(K key) {
      synchronized (mutex) {

      return (NavigableMap<K, V>) super.delegate();
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> ceilingEntry(K key) {
      synchronized (mutex) {
        return nullableSynchronizedEntry(delegate().ceilingEntry(key), mutex);
      }
    }

    @Override
    @CheckForNull
    public K ceilingKey(K key) {
      synchronized (mutex) {