private void UpdateExistingSpecification(IEnumerable <PriceSpecification> specifications)
        {
            var existingJuiceInfo = specifications.Where(
                s => JuiceStockDataCollection.All(c => c.Name == s.Name));

            foreach (var specification in existingJuiceInfo)
            {
                var spec = JuiceStockDataCollection.First(data => data.Name == specification.Name);
                spec.Price  = specification.Price;
                spec.CanBuy = _vendingMachine.CanBuy(specification.Name);
            }
        }
        private void AddSpecification(IEnumerable <PriceSpecification> specifications)
        {
            var newJuiceInfo = specifications.Where(
                s => JuiceStockDataCollection.All(c => c.Name != s.Name));


            foreach (var specification in newJuiceInfo)
            {
                JuiceStockDataCollection.Add(
                    new JuiceStockData
                {
                    Name   = specification.Name,
                    Price  = specification.Price,
                    CanBuy = _vendingMachine.CanBuy(specification.Name)
                });
            }
        }