public void UpdateTest()
        {
            var firstProduct = _db.Products.First();

            firstProduct.Price += 100;
            DateTime now = DateTime.Now;

            _store.Update(firstProduct);

            var changedProduct = _db.Products.FirstOrDefault(p => p.Id == firstProduct.Id);

            Assert.IsNotNull(changedProduct);
            Assert.AreEqual(firstProduct.Price, changedProduct.Price);
            Assert.IsTrue(changedProduct.LastUpdate >= now);
        }
 public Product Put(string sku, Product product)
 {
     _productStore.Update(product, sku);
     return(product);
 }