public void CalculateDividendYieldForCommonStockTest()
{
var stockCommon = new CommonStock {
symbol = "TEA", lastDividend = 10, parValue = 100
};
var currentDividendCommon = exchangeStock.CalculateDividendYield(stockCommon, 100);
var expectedDividendYield = 0.1;
Assert.AreEqual(expectedDividendYield, currentDividendCommon);
}