     }
 
     do {
+      let sportCar = SportCar(context: context)
       let expensiveSportCar = ExpensiveSportCar(context: context)
-      let sportCar = SportCar(context: context)
-
+     
       let ancestorCommontEntity = sportCar.entity.commonEntityAncestor(with: expensiveSportCar.entity)
       XCTAssertNotNil(ancestorCommontEntity)
       XCTAssertTrue(ancestorCommontEntity == sportCar.entity)

      XCTAssertNotNil(ancestorCommontEntity)
      XCTAssertTrue(ancestorCommontEntity == car.entity)
    }

    do {
      let sportCar = SportCar(context: context)

  }


  func testEntitiesKeepingOnlyCommonEntityAncestors() {
    let stack = CoreDataStack()!
    let context = stack.mainContext

