@Test public void calculateCheckDigit() {

    CitizenId cid;
    cid = new CitizenId("161025581111");
    assertEquals("calculate check digit result should be 2", 2, cid.calculateCheckDigit());
    cid = new CitizenId("161025580000");
    assertEquals("calculate check digit result should be 5", 5, cid.calculateCheckDigit());
}