public static Builder newBuilder() {
    return new Builder();
  }
@Test void localEndpointDefaults() {
    Tracing tracing = Tracing.newBuilder().build();
    assertThat(tracing).extracting("tracer.pendingSpans.defaultSpan.localServiceName")
      .isEqualTo("unknown");
    assertThat(tracing).extracting("tracer.pendingSpans.defaultSpan.localIp")
      .isEqualTo(Platform.get().linkLocalIp());
  }