*
   * @throws IllegalArgumentException if {@code hashCodes} is empty, or the hash codes do not all
   *     have the same bit length
   */
  public static HashCode combineUnordered(Iterable<HashCode> hashCodes) {
    Iterator<HashCode> iterator = hashCodes.iterator();
    checkArgument(iterator.hasNext(), "Must be at least 1 hash code to combine.");

    assertEquals(
        HashCode.fromInt(96), Hashing.combineUnordered(ImmutableList.of(hash32, hash32, hash32)));
    assertEquals(
        Hashing.combineUnordered(ImmutableList.of(hash31, hash32)),
        Hashing.combineUnordered(ImmutableList.of(hash32, hash31)));
  }

  public void testCombineUnordered_randomHashCodes() {
    Random random = new Random(RANDOM_SEED);