public void testHashCode_containingNull() {
    Collection<E> elements = getSampleElements(getNumElements() - 1);
    int expectedHashCode = 0;
    for (E element : elements) {
      expectedHashCode += ((element == null) ? 0 : element.hashCode());
    }

    elements.add(null);
    collection = getSubjectGenerator().create(elements.toArray());
    assertEquals(

            String url = element.'@url'
            if (url.startsWith('website:')) {
                url = url.substring(8)
                url = "${websiteUrl.get()}/${url}"
                element.setAttribute('url', url)
            }
        }
    }

    static def findAll(Document doc, String byName) {
        doc.documentElement.depthFirst().findAll { it.name() == byName }
    }

  public E floor(E element) {
    int index = headIndex(element, true) - 1;
    return (index == -1) ? null : elements.get(index);
  }

  @Override
  @CheckForNull
  public E ceiling(E element) {
    int index = tailIndex(element, true);
    return (index == size()) ? null : elements.get(index);
  }

  @Override
  @CheckForNull
  public E higher(E element) {
    int index = tailIndex(element, false);

    private static final Pattern HTML_ELEMENT = Pattern.compile("(?s)<\\\\?[^<]+?>");
    private static final Pattern ELEMENT_ATTRIBUTE = Pattern.compile("(?s)\\w+(\\s*=\\s*('.*?')|(\".*?\"))?");
    private static final Pattern END_ATTRIBUTE_NAME = Pattern.compile("=|(\\s)|(/>)|>");
    private static final Pattern ATTRIBUTE_SEPARATOR = Pattern.compile("\\s*=\\s*");
    private static final Pattern END_ELEMENT_NAME = Pattern.compile("\\s+|(/>)|>");

  @Override
  public int indexOf(@CheckForNull Object element) {
    return delegate().indexOf(element);
  }

  @Override
  public int lastIndexOf(@CheckForNull Object element) {
    return delegate().lastIndexOf(element);
  }

  @Override
  public ListIterator<E> listIterator() {
    return delegate().listIterator();
  }

  @Override
  public ListIterator<E> listIterator(int index) {

    if (occurrences == 0) {
      return count(element);
    }
    checkArgument(occurrences > 0, "occurrences cannot be negative: %s", occurrences);
    int entryIndex = backingMap.indexOf(element);
    if (entryIndex == -1) {
      backingMap.put(element, occurrences);
      size += occurrences;
      return 0;
    }
    int oldCount = backingMap.getValue(entryIndex);

    assertEquals("Should be able to peek() at first element", "A", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() first element multiple times", "A", peekingIterator.peek());
    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(

    }

    @Override
    public boolean add(@ParametricNullness E element) {
      checkArgument(predicate.apply(element));
      return unfiltered.add(element);
    }

    @Override
    public boolean addAll(Collection<? extends E> collection) {
      for (E element : collection) {
        checkArgument(predicate.apply(element));
      }
      return unfiltered.addAll(collection);
    }

      for (int i = 0; i < 100; i++) {
        Element element = Element.values()[random.nextInt(range)];
        elements.add(element);
        queue.add(element);
      }
      Iterator<Element> queueIterator = queue.iterator();
      int remaining = queue.size();
      while (queueIterator.hasNext()) {
        Element element = queueIterator.next();
        remaining--;

        }

        Document document = parent.getOwnerDocument();

        Element section = document.createElement("section");
        parent.appendChild(section);

        Element title = document.createElement("title");
        section.appendChild(title);
        title.appendChild(document.createTextNode("Methods added by the "));
        Element literal = document.createElement("literal");
        title.appendChild(literal);