public void CanCalculateCheckDigit() { int check = Ean13.CalculateCheckDigit("890400021003"); Assert.AreEqual(7, check); check = Ean13.CalculateCheckDigit("201000450000"); Assert.AreEqual(8, check); check = Ean13.CalculateCheckDigit("978020113447"); Assert.AreEqual(6, check); }