public void ChangeIterestTest()
{
Client client = new Client("Jan", "Nowak", "01234567891");
Investment investment = new Investment("123", new InterestTenPercent(), 1000, client);
investment.AddIterest();
investment.ChangeIterest(new InterestFivePercent());
investment.AddIterest();
Assert.AreEqual(1155, investment.GetSaldo());
}