RsId { @Override public String toString() { if (id == EMPTY.id) { return VCF_EMPTY_VALUE; } return "rs" + id; } private  RsId(int id); static RsId of(int id); static RsId of(String id); static RsId empty(); int getId(); boolean isEmpty(); @Override int hashCode(); @Override boolean equals(Object o); @Override String toString();  }
@Test public void testToString() { assertThat(instance.toString(), equalTo("rs234567364")); }