*  / \\
   * b   c
   *  \ /
   *   d<>
   * }</pre>
   *
   * {@code <>} indicates a self-loop
   */
  private static final SuccessorsFunction<Character> MULTI_GRAPH =
      createDirectedGraph("aa", "dd", "ab", "ac", "ca", "cd", "bd");

  /** A directed graph with a single cycle: a -> b -> c -> d -> a. */
  private static final SuccessorsFunction<Character> CYCLE_GRAPH =
      createDirectedGraph("ab", "bc", "cd", "da");

                  @Override
                  public SampleElements<Entry<String, Integer>> samples() {
                    return new SampleElements<>(
                        mapEntry("a", 1),
                        mapEntry("aa", 2),
                        mapEntry("aba", 3),
                        mapEntry("bbbb", 4),
                        mapEntry("ccccc", 5));
                  }

                  @Override

   *  / \\
   * b   c
   *  \ /
   *   d<>
   * }</pre>
   *
   * {@code <>} indicates a self-loop
   */
  private static final SuccessorsFunction<Character> MULTI_GRAPH =
      createDirectedGraph("aa", "dd", "ab", "ac", "ca", "cd", "bd");

  /** A directed graph with a single cycle: a -> b -> c -> d -> a. */
  private static final SuccessorsFunction<Character> CYCLE_GRAPH =
      createDirectedGraph("ab", "bc", "cd", "da");

iart?trahc??o&htua?tacude???s&citsigol?e&civres?r??krow?serp!xe??tnega??t&farcr&ia?otor??hgil&f?orcim??liubemoh?n&atlusnoc?e&duts?m&esuma?n&iatretne?revog??piuqe????olip?ropria?si&lanruoj?tneics???w&erc?ohs??y&cnegreme?dobper?tefas????rref?z??p!.&a&aa?ca?pc??dem?ecartsnd.icb,gne?korgn,r&ab?uj??s&nduolc,rahc21,?t&acova?cca?hcer??wal?ysrab,???s!.&em?gro?hcs,moc?syevrus,ten?ude?vog???t!.&0x,116,ayo,gro?lim?moc?nayn,sulpnpv,t&cennockciuq.tcerid,en??ude?v&dr,og???o&hp?m?v?yk??tol?ua??v&iv?lov??xas?yk...