@Test protected void dependencies_headlessTrace(TestInfo testInfo) throws Exception {
    String testSuffix = testSuffix(testInfo);
    ArrayList<Span> trace = new ArrayList<>(newTrace(testSuffix));
    trace.remove(0);
    processDependencies(trace);

    assertThat(store().getDependencies(endTs(trace), DAY).execute())
      .containsExactlyInAnyOrderElementsOf(links(testSuffix));
  }
Some systems log a different trace id than the root span. This seems "headless", as we won't
see a span whose id is the same as the trace id.
zipkin-tests/src/main/java/zipkin2/storage/ITDependencies.java