public void SellInvestment() { // Arrange StockEngine engine = new YahooStockEngine(); IEnumerable<Quote> stocks = engine.AllQuotes(); Investment investment = new Investment() { Id = Guid.NewGuid() }; decimal newPrice = 1.1m; // Act engine.SellInvestment(investment.Id, newPrice, SellReason.HighPrice, DateTime.Today); // Assert }