public void testElement_empty() {
    assertThrows(NoSuchElementException.class, () -> getQueue().element());
    expectUnchanged();
  }

  @CollectionSize.Require(ONE)
  public void testElement_size1() {
    assertEquals("size1Queue.element() should return first element", e0(), getQueue().element());
    expectUnchanged();
  }

  @CollectionFeature.Require(KNOWN_ORDER)
  @CollectionSize.Require(SEVERAL)

  @Override
  void setCountCheckReturnValue(E element, int count) {
    assertEquals(
        "multiset.setCount() should return the old count",
        getMultiset().count(element),
        setCount(element, count));
  }

  @Override
  void setCountNoCheckReturnValue(E element, int count) {
    setCount(element, count);
  }

  @CanIgnoreReturnValue
  private int setCount(E element, int count) {

  static int indexOfImpl(List<?> list, @Nullable Object element) {
    if (list instanceof RandomAccess) {
      return indexOfRandomAccess(list, element);
    } else {
      ListIterator<?> listIterator = list.listIterator();
      while (listIterator.hasNext()) {
        if (Objects.equals(element, listIterator.next())) {
          return listIterator.previousIndex();
        }
      }

    /**
     * Return the index of the next lower element in the list, or {@code -1} if there is no such
     * element.
     */
    NEXT_LOWER {
      @Override
      int resultIndex(int higherIndex) {
        return higherIndex - 1;
      }
    },
    /**
     * Return the index of the next higher element in the list, or {@code list.size()} if there is
     * no such element.
     */
    NEXT_HIGHER {

  static int indexOfImpl(List<?> list, @Nullable Object element) {
    if (list instanceof RandomAccess) {
      return indexOfRandomAccess(list, element);
    } else {
      ListIterator<?> listIterator = list.listIterator();
      while (listIterator.hasNext()) {
        if (Objects.equals(element, listIterator.next())) {
          return listIterator.previousIndex();
        }
      }

    /**
     * Returns true if this set contains the specified element.
     *
     * @param o
     *            element whose presence in this set is to be tested.
     * @return true if this set contains the specified element.
     */
    @Override
    public boolean contains(final Object o) {
        return map.containsKey(o);
    }

    /**
     * Adds the specified element to this set if it is not already present.
     *

   * Returns an {@link Optional} containing the first element in this fluent iterable. If the
   * iterable is empty, {@code Optional.absent()} is returned.
   *
   * <p><b>{@code Stream} equivalent:</b> if the goal is to obtain any element, {@link
   * Stream#findAny}; if it must specifically be the <i>first</i> element, {@code Stream#findFirst}.
   *
   * @throws NullPointerException if the first element is null; if this is a possibility, use {@code

      }
    }

    /**
     * Adds {@code element} to the {@code ImmutableSet}. If the {@code ImmutableSet} already
     * contains {@code element}, then {@code add} has no effect (only the previously added element
     * is retained).
     *
     * @param element the element to add
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code element} is null
     */
    @Override

    }

    /**
     * Adds {@code element} to the {@code ImmutableSortedSet}. If the {@code ImmutableSortedSet}
     * already contains {@code element}, then {@code add} has no effect. (only the previously added
     * element is retained).
     *
     * @param element the element to add
     * @return this {@code Builder} object
     * @throws NullPointerException if {@code element} is null
     */
    @CanIgnoreReturnValue

  /** Returns {@code true} if {@code iterator} contains {@code element}. */
  public static boolean contains(Iterator<?> iterator, @Nullable Object element) {
    if (element == null) {
      while (iterator.hasNext()) {
        if (iterator.next() == null) {
          return true;
        }
      }
    } else {
      while (iterator.hasNext()) {
        if (element.equals(iterator.next())) {
          return true;
        }