@Test
 public void shouldCalculateCommonPrefixLength() {
   Ipv4 ipv4 = Ipv4.of("192.168.0.0");
   assertEquals(0, ipv4.getCommonPrefixLength(Ipv4.of("0.0.0.0")));
   assertEquals(16, ipv4.getCommonPrefixLength(Ipv4.of("192.168.255.255")));
   assertEquals(32, ipv4.getCommonPrefixLength(Ipv4.of("192.168.0.0")));
 }