public DBFixture addEngine(EngineType engineType) {
   currentEngine = new Engine();
   engines.add(currentEngine);
   currentEngine.setType(engineType);
   currentVehicle.setEngine(currentEngine);
   currentEngine.setManufacturer(currentManufacturer);
   return this;
 }
 public DBFixture ownedByManufacturer() {
   currentManufacturer.getOwnedEngines().add(currentEngine);
   currentEngine.setManufacturer(currentManufacturer);
   return this;
 }