@Test public void should_add_b3_single_header_to_message() {

  Message message = MessageBuilder.withBody(new byte[0]).build();
  Message postProcessMessage = tracingMessagePostProcessor.postProcessMessage(message);
  assertThat(postProcessMessage.getMessageProperties().getHeaders())
    .containsOnlyKeys("b3");
  assertThat(postProcessMessage.getMessageProperties().getHeaders().get("b3").toString())
    .matches("^[0-9a-f]{16}-[0-9a-f]{16}-1$");
}