public void SetPaymentCardNumberTest() { // Arrange byte[] derivedKey = new byte[16] { 111, 222, 31, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 104, 15, 16 }; SymmetricKeyAlgorithm ska = SymmetricKeyAlgorithm.GenerateNew(SymmetricEncryptionAlgorithm.AES_CTR); PaymentCard paymentCard = new PaymentCard("Bank of Dragon", "Cool Dragon", "Debit", "0000000000001234", "111", "11/20", "05/33", "Super cool card I have here"); PaymentCardSecret paymentCardSecret = new PaymentCardSecret(paymentCard, "does not matter", ska, derivedKey); string number = "1234500000001234"; // Act bool shouldBeTrue = paymentCardSecret.SetNumber(number, derivedKey); string numberAfterModification = paymentCardSecret.GetNumber(derivedKey); bool shouldBeFalse = paymentCardSecret.SetNumber(number, new byte[] { 1, 2, 3 }); // Assert Assert.IsTrue(shouldBeTrue); Assert.IsFalse(shouldBeFalse); Assert.IsFalse(string.IsNullOrEmpty(numberAfterModification)); Assert.AreEqual(number, numberAfterModification); }