public Span handleSendWithParent(RpcClientRequest request, @Nullable TraceContext parent) {
    if (request == null) throw new NullPointerException("request == null");
    return handleSend(request, tracer.nextSpanWithParent(sampler, request, parent));
  }
@Test void handleSendWithParent_overrideNull() {
    try (Scope scope = httpTracing.tracing.currentTraceContext().newScope(null)) {
      brave.Span span = handler.handleSendWithParent(request, context);

      // If the overwrite was successful, we have a child span.
      assertThat(span.context().parentIdAsLong()).isEqualTo(context.spanId());
    }
  }