public void Modulus10_WhenStringHasInvalidLength_ThrowsException(string chars)
{
// Arrange
// Act
// Assert
Assert.That(() => CalcUtility.CheckDigitForIsbn13(chars), Throws.InstanceOf <ArgumentException>());
}
public char Modulus10_WhenStringHasValidLength_ReturnsCheckDigit(string chars)
{
// Arrange
var digits = Regex.Replace(chars, "[^0-9]+", string.Empty).Take(12);
// Act
// Assert
return(CalcUtility.CheckDigitForIsbn13(digits));
}