@Test void builder_merge_remoteEndpoint_merge() {
    Span merged = Span.newBuilder().remoteEndpoint(Endpoint.newBuilder().serviceName("a").build())
      .merge(
        base.toBuilder().remoteEndpoint(Endpoint.newBuilder().ip("192.168.99.101").build()).build())
      .merge(
        base.toBuilder().remoteEndpoint(Endpoint.newBuilder().ip("2001:db8::c001").build()).build())
      .merge(
        base.toBuilder().remoteEndpoint(Endpoint.newBuilder().port(80).build()).build())
      .build();

    assertThat(merged).isEqualToComparingFieldByField(
      base.toBuilder().remoteEndpoint(Endpoint.newBuilder()
        .serviceName("a")
        .ip("192.168.99.101")
        .ip("2001:db8::c001")
        .port(80)
        .build()
      ).build()
    );
  }
Catches common error when zero is passed instead of null for a timestamp
zipkin/src/test/java/zipkin2/SpanTest.java