/// <function cref ="eCommerce_14a.StoreManagment.decraseProductAmount(int, string, int, int)
        public void TestDecraseProductAmount_nonExistingUser()
        {
            Tuple <bool, string> decraseRes = storeManagment.decraseProductAmount(1, "shimon", 1, 1, false);

            if (decraseRes.Item1)
            {
                Assert.Fail();
            }
            Assert.AreEqual(CommonStr.StoreMangmentErrorMessage.userNotFoundErrMsg, decraseRes.Item2);
        }
 /// <req> https://github.com/chendoy/wsep_14a/wiki/Use-cases#use-case-store-manager---increasedecrease-amount-511 </req>
 /// <req> https://github.com/chendoy/wsep_14a/wiki/Use-cases#use-case-inventory-management---increasedecrease-amount-414- </req>
 public Tuple <bool, string> decraseProduct(int storeId, string userName, int productId, int amount)
 {
     return(storeManagment.decraseProductAmount(storeId, userName, productId, amount));
 }