public void Test_VerifyCheckSum()
{
var serialNumber = SerialNumber.Create("ABC");
Assert.IsTrue(SerialNumber.IsCheckSumValid(serialNumber));
var modified = "D" + new string(serialNumber.Skip(1).ToArray());
Assert.IsFalse(SerialNumber.IsCheckSumValid(modified));
Assert.IsFalse(SerialNumber.IsCheckSumValid(modified + "A"));
TestHelper.AssertException <ArgumentNullException>(() => SerialNumber.IsCheckSumValid(null));
Assert.IsFalse(SerialNumber.IsCheckSumValid(""));
Assert.IsFalse(SerialNumber.IsCheckSumValid("ABCDER"));
}