    @Test
    public void canBuildAnFullInternalLetterWithReverseArrow() throws Exception {

        IOTransition.IOLetter letter = Messages.fullLetter("^a<-b.m");

        Assertions.assertThat(letter.label.toString()).isEqualTo("b -> a.m");
        Assertions.assertThat(letter.type).isEqualTo(IOAlphabetType.INTERNAL);
    }