public void Modulus11_WhenStringHasInvalidLength_ThrowsException(string chars)
{
// Arrange
// Act
// Assert
Assert.That(() => CalcUtility.CheckDigitForIsbn10(chars), Throws.InstanceOf <ArgumentException>());
}
public char Modulus11_WhenStringHasValidLength_ReturnsCheckDigit(string chars)
{
// Arrange
var digits = Regex.Replace(chars, "[^0-9]+", string.Empty).Take(9);
// Act
// Assert
return(CalcUtility.CheckDigitForIsbn10(digits));
}