public void TestStockMarket()
{
Assert.Throws <KeyNotFoundException>(() => StockMarket.GetExchangeRates(StockMarketCurrency.Rub));
Assert.InRange(StockMarket.GetExchangeRates(StockMarketCurrency.Eur), 20, 200);
Assert.InRange(StockMarket.GetExchangeRates(StockMarketCurrency.Usd), 20, 200);
}