@Test
public void shouldCreateFunctionFromItemToListWithThenFilter() {

  final Function<String, List<Character>> function = functionFrom(String.class)
      .apply(new DoubleString())
      .unpack(new StringToListChar())
      .thenFilter(new CharacterFilter('n'));
  assertThat(function.apply(INPUT_STRING), contains('n', 'n'));
}