@Test public void testThatCurrentSpanIsAnnotatedWithKeyValue(){
  final SpanId spanId=SpanId.fromRandom();
  final Response r=createWebClient("/bookstore/book/1").header(TracerHeaders.DEFAULT_HEADER_SPAN_ID,spanId.toString()).get();
  assertEquals(Status.OK.getStatusCode(),r.getStatus());
  assertThat(TestSpanReceiver.getAllSpans().size(),equalTo(1));
  assertThat(TestSpanReceiver.getAllSpans().get(0).getDescription(),equalTo("GET bookstore/book/1"));
  assertThat(TestSpanReceiver.getAllSpans().get(0).getKVAnnotations().size(),equalTo(1));
  assertThat((String)r.getHeaders().getFirst(TracerHeaders.DEFAULT_HEADER_SPAN_ID),equalTo(spanId.toString()));
}