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()));
  }

  @CollectionSize.Require(SEVERAL)
  public void testHigher() {

    }
  }

  @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() {
    delegate.clear();
  }

  @Override
  public Comparator<? super K> comparator() {

      @SuppressWarnings({"unchecked", "nullness"})
      SortedMap<@Nullable Object, V> self = (SortedMap<@Nullable Object, V>) this;
      Object ceilingKey = self.tailMap(key).firstKey();
      return unsafeCompare(comparator(), ceilingKey, key) == 0;
    } catch (ClassCastException | NoSuchElementException | NullPointerException e) {
      return false;
    }
  }

  /**

    }
  }

  @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() {
    delegate.clear();
  }

  @Override
  public Comparator<? super K> comparator() {

  }

  @Override
  public @Nullable K floorKey(@ParametricNullness K key) {
    return Maps.keyOrNull(floorEntry(key));
  }

  @Override
  public @Nullable K ceilingKey(@ParametricNullness K key) {
    return Maps.keyOrNull(ceilingEntry(key));
  }

  @Override
  public @Nullable K higherKey(@ParametricNullness K key) {
    return Maps.keyOrNull(higherEntry(key));
  }

  }

  @Override
  public @Nullable K floorKey(@ParametricNullness K key) {
    return Maps.keyOrNull(floorEntry(key));
  }

  @Override
  public @Nullable K ceilingKey(@ParametricNullness K key) {
    return Maps.keyOrNull(ceilingEntry(key));
  }

  @Override
  public @Nullable K higherKey(@ParametricNullness K key) {
    return Maps.keyOrNull(higherEntry(key));
  }

      return standardFloorKey(key);
    }

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

    @Override
    public @Nullable K ceilingKey(K key) {
      return standardCeilingKey(key);
    }

    @Override
    public @Nullable Entry<K, V> higherEntry(K key) {
      return standardHigherEntry(key);
    }

    @Override