int nestingDepth = 128;
    Iterator<Integer> iterator = iterateOver();
    for (int i = 0; i < nestingDepth; i++) {
      iterator = Iterators.concat(iterator, iterateOver(1));
    }
    assertEquals(nestingDepth, Iterators.size(iterator));
  }

  public void testConcatNested_appendToBeginning() {
    int nestingDepth = 128;
    Iterator<Integer> iterator = iterateOver();

    int nestingDepth = 128;
    Iterator<Integer> iterator = iterateOver();
    for (int i = 0; i < nestingDepth; i++) {
      iterator = Iterators.concat(iterator, iterateOver(1));
    }
    assertEquals(nestingDepth, Iterators.size(iterator));
  }

  public void testConcatNested_appendToBeginning() {
    int nestingDepth = 128;
    Iterator<Integer> iterator = iterateOver();

   */
  public static CharMatcher breakingWhitespace() {
    return BreakingWhitespace.INSTANCE;
  }

  /**
   * Determines whether a character is ASCII, meaning that its code point is less than 128.
   *
   * @since 19.0 (since 1.0 as constant {@code ASCII})
   */
  public static CharMatcher ascii() {
    return Ascii.INSTANCE;
  }

  /**