public void Should_NotBeAbleToMakePaymentWith_InsufficentFunds()
{
var card = new PaymentCard();
card.TopUp(10);
Assert.Throws <Exception>(() => card.MakePayment(20));
}
public void Should_BeAbleTo_MakeAPayment()
{
var card = new PaymentCard();
card.TopUp(10);
card.MakePayment(10);
Assert.That(card.Balance, Is.EqualTo(0));
}