       XCTAssertNotNil(ancestorCommontEntity)
       XCTAssertTrue(ancestorCommontEntity == car.entity)
     }
+    
+    do {
+      let car = Car(context: context)
+      let sportCar = SportCar(context: context)
+      
+      let ancestorCommontEntity = car.entity.commonEntityAncestor(with: sportCar.entity)
+      XCTAssertNotNil(ancestorCommontEntity)
+      XCTAssertTrue(ancestorCommontEntity == car.entity)
+    }
 
     do {
       let sportCar = SportCar(context: context)

  }


  func test2() {
    let stack = CoreDataStack()!
    let context = stack.mainContext


    }

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