public function testDeleteQty()
 {
     $product = new Product();
     $product->setQty(6);
     $item = new Item();
     $item->setQty(4);
     $item->setProduct($product);
     PurchaseItemManager::deleteQty($item);
     $this->assertEquals(2, $item->getProduct()->getQty(), "Unexpected value for qty in product for deleteQty method ");
 }