@Test public void on_completion_should_finish_span() {

  Span span = tracing.tracer().nextSpan().start();
  Callback tracingCallback = TracingCallback.create(null, span, currentTraceContext);
  tracingCallback.onCompletion(createRecordMetadata(), null);
  assertThat(spans.get(0).finishTimestamp()).isNotZero();
}