@Test protected void allShouldWorkWhenEmpty() throws Exception {
    QueryRequest.Builder q = requestBuilder().serviceName("service");
    assertGetTracesReturnsEmpty(q.build());
    assertGetTracesReturnsEmpty(q.remoteServiceName("remotey").build());
    assertGetTracesReturnsEmpty(q.spanName("methodcall").build());
    assertGetTracesReturnsEmpty(q.parseAnnotationQuery("custom").build());
    assertGetTracesReturnsEmpty(q.parseAnnotationQuery("BAH=BEH").build());
  }
This would only happen when the store layer is bootstrapping, or has been purged.
zipkin-tests/src/main/java/zipkin2/storage/ITSpanStore.java