* splitToString automatically.
   */
  public void testCharacterSimpleSplitToList() {
    String simple = "a,b,c";
    List<String> letters = COMMA_SPLITTER.splitToList(simple);
    assertThat(letters).containsExactly("a", "b", "c").inOrder();
  }

  public void testCharacterSimpleSplitToStream() {
    String simple = "a,b,c";

   * splitToString automatically.
   */
  public void testCharacterSimpleSplitToList() {
    String simple = "a,b,c";
    List<String> letters = COMMA_SPLITTER.splitToList(simple);
    assertThat(letters).containsExactly("a", "b", "c").inOrder();
  }

  public void testToString() {
    assertEquals("[]", COMMA_SPLITTER.split("").toString());