public Span handleSend(HttpClientRequest request) {
    if (request == null) throw new NullPointerException("request == null");
    return handleSend(request, tracer.nextSpan(httpSampler, request));
  }
@Test void handleSend_samplerSeesHttpClientRequest() {
    SamplerFunction<HttpRequest> clientSampler = mock(SamplerFunction.class);
    init(httpTracingBuilder(tracingBuilder()).clientSampler(clientSampler));

    handler.handleSend(request);

    verify(clientSampler).trySample(request);
  }