@Test void ip_ipv6_addr() throws Exception {
    String ipv6 = "2001:db8::c001";
    Endpoint endpoint = Endpoint.newBuilder().ip(Inet6Address.getByName(ipv6)).build();

    assertThat(endpoint.ipv4())
      .isNull();
    assertThat(endpoint.ipv4Bytes())
      .isNull();
    assertThat(endpoint.ipv6())
      .isEqualTo(ipv6);
    assertThat(endpoint.ipv6Bytes())
      .containsExactly(Inet6Address.getByName(ipv6).getAddress());
  }
Many getPort operations return -1 by default. Leniently coerse to null.
zipkin/src/test/java/zipkin2/EndpointTest.java