public void TestNameTest(double balance, int year, double expected)
{
var goldCard = new GoldCard("", "", balance, year);
double calcCouponValue = goldCard.CalcCouponValue();
Assert.AreEqual(expected, calcCouponValue);
}
// add more test cases so all rules are defined
public void CalcCouponValue_should_calculate_correctly(double balance, double year, double expectedResult)
{
// arrange your test (sut == system under test)
var sut = new GoldCard(null, null, balance, year);
// act (execute the test)
var actualResult = sut.CalcCouponValue();
// assert (verify that what you get is what you want)
Assert.That(actualResult, Is.EqualTo(expectedResult);
}