@Test void builder_merge_localEndpoint_null() {
    Span merged = Span.newBuilder().localEndpoint(FRONTEND)
      .merge(Span.newBuilder().traceId(base.traceId()).id(base.id()).build()).build();

    assertThat(merged).isEqualToComparingFieldByField(
      Span.newBuilder().traceId(base.traceId()).id(base.id()).localEndpoint(FRONTEND).build()
    );
  }
Catches common error when zero is passed instead of null for a timestamp
zipkin/src/test/java/zipkin2/SpanTest.java