String simple = "abcd";
    Iterable<String> letters = Splitter.fixedLength(1).split(simple);
    assertThat(letters).containsExactly("a", "b", "c", "d").inOrder();
  }

  public void testFixedLengthSplitZeroChunkLen() {
    assertThrows(IllegalArgumentException.class, () -> Splitter.fixedLength(0));
  }

  public void testFixedLengthSplitNegativeChunkLen() {