public void TestHandlesUnknownProductsGracefully() { MockProduct mockProduct = new MockProduct(); ProductStock productStock = new ProductStock(); MockProductStockObserver mockProductStockObserver = new MockProductStockObserver(); productStock.RegisterObserver(mockProductStockObserver); productStock.Remove(mockProduct); Assert.AreEqual(0, productStock.Count(mockProduct)); Assert.AreEqual(0, mockProductStockObserver.NumberOfTimesProductStockUpdatedWasCalled); }