static Iterable<? extends DependencyLink> links(String testSuffix) {
    String frontend = appendSuffix(TestObjects.FRONTEND.serviceName(), testSuffix);
    String backend = appendSuffix(TestObjects.BACKEND.serviceName(), testSuffix);
    String db = appendSuffix(TestObjects.DB.serviceName(), testSuffix);
    return List.of(
      DependencyLink.newBuilder().parent(frontend).child(backend).callCount(1L).build(),
      DependencyLink.newBuilder().parent(backend).child(db).callCount(1L).errorCount(1L).build()
    );
  }
Default links produced by {@link TestObjects#newTrace(String)}
zipkin-tests/src/main/java/zipkin2/storage/ITDependencies.java