@Test
void mapChar() {

    final ToChar<Character> toChar = c -> c;
    final ToCharMapper<Character, ToChar<Character>, CharUnaryOperator> toCharMapper =
            (ToCharMapper<Character, ToChar<Character>, CharUnaryOperator>)
                    MapperUtil.mapChar(toChar, c -> c);
    assertEquals(MapperType.CHAR_TO_CHAR, toCharMapper.mapperType());
}