public void VisaIsValid() { var visaNumbers = new[] { "4444 4444 4444 4448", "4444 4244 4444 4440", "4444 4144 4444 4441", "4012 8888 8888 1881", "4055 0111 1111 1111" }; foreach (var cardNumber in visaNumbers) { AssertIsValid(cardNumber); } }