}
    }.test();
  }

  public void testContainsAll_sameType() {
    Collection<String> c = of("a", "b", "c");
    assertFalse(c.containsAll(of("a", "b", "c", "d")));
    assertFalse(c.containsAll(of("a", "d")));
    assertTrue(c.containsAll(of("a", "c")));
    assertTrue(c.containsAll(of("a", "b", "c")));
  }

  public void testEquals_sameType() {
    Collection<String> c = of("a", "b", "c");

    return comparator;
  }

  @Override
  public boolean contains(Object object) {
    return delegate.contains(checkValid(object));
  }

  @Override
  public boolean containsAll(Collection<?> c) {
    return delegate.containsAll(c);
  }

  @Override
  public Iterator<E> descendingIterator() {
    return delegate.descendingIterator();
  }

  @Override
  public NavigableSet<E> descendingSet() {

      public boolean contains(@Nullable Object object) {
        return set1.contains(object) && set2.contains(object);
      }

      @Override
      public boolean containsAll(Collection<?> collection) {
        return set1.containsAll(collection) && set2.containsAll(collection);
      }

      @Override
      int minSize() {
        return 0;
      }

      @Override
      int maxSize() {

            return parent.add(e);
        }

        public boolean remove(final Object o) {
            return parent.remove(o);
        }

        public boolean containsAll(final Collection<?> c) {
            return parent.containsAll(c);
        }

        public boolean addAll(final Collection<? extends E> c) {
            return parent.addAll(c);
        }

                public boolean remove(Object o) {
                  return map.entrySet().remove(o);
                }

                @Override
                public boolean containsAll(Collection<?> c) {
                  return map.entrySet().containsAll(c);
                }

                @Override
                public boolean removeAll(Collection<?> c) {
                  return map.entrySet().removeAll(c);

    public void clear() {
      standardClear();
    }

    @Override
    public boolean contains(Object object) {
      return standardContains(object);
    }

    @Override
    public boolean containsAll(Collection<?> collection) {
      return standardContainsAll(collection);
    }

    @Override
    public boolean remove(Object object) {
      return standardRemove(object);
    }

    @Override

    public void clear() {
      standardClear();
    }

    @Override
    public boolean contains(Object object) {
      return standardContains(object);
    }

    @Override
    public boolean containsAll(Collection<?> collection) {
      return standardContainsAll(collection);
    }

    @Override
    public boolean remove(Object object) {
      return standardRemove(object);
    }

    @Override

   */

  @Override
  public boolean equals(@Nullable Object object) {
    if (object instanceof Set) {
      Set<?> that = (Set<?>) object;
      return (this.size() == that.size()) && this.containsAll(that);
    }
    return false;
  }

  @Override
  public int hashCode() {
    int hashCodeSum = 0;
    for (Object o : this) {
      hashCodeSum += (o == null) ? 0 : o.hashCode();
    }

   */

  @Override
  public boolean equals(@Nullable Object object) {
    if (object instanceof Set) {
      Set<?> that = (Set<?>) object;
      return (this.size() == that.size()) && this.containsAll(that);
    }
    return false;
  }

  @Override
  public int hashCode() {
    int hashCodeSum = 0;
    for (Object o : this) {
      hashCodeSum += (o == null) ? 0 : o.hashCode();
    }

    public void clear() {
      standardClear();
    }

    @Override
    public boolean contains(Object object) {
      return standardContains(object);
    }

    @Override
    public boolean containsAll(Collection<?> collection) {
      return standardContainsAll(collection);
    }

    @Override
    public boolean remove(Object object) {
      return standardRemove(object);
    }

    @Override