@Override public synchronized Call<List<String>> getSpanNames(String service) {
    if (service.isEmpty() || !searchEnabled) return Call.emptyList();
    service = service.toLowerCase(Locale.ROOT); // service names are always lowercase!
    return Call.create(new ArrayList<>(serviceToSpanNames.get(service)));
  }
Used for testing. Returns all dependency links unconditionally.
zipkin/src/main/java/zipkin2/storage/InMemoryStorage.java