public void NormalizeForAnyCountry_ValidNationalIdentifier_ReturnsNormalizedValue(
            string nationalIdentifier, string expected)
        {
            var result = NationalIdentifierValidator.NormalizeForAnyCountry(nationalIdentifier);

            Assert.That(result, Is.EqualTo(expected));
        }
        public void NormalizeForAnyCountry_InvalidNationalIdentifier_ThrowsArgumentException(string nationalIdentifier)
        {
            var ex = Assert.Throws <ArgumentException>(() => NationalIdentifierValidator.NormalizeForAnyCountry(nationalIdentifier));

            Assert.That(ex.ParamName, Is.EqualTo("nationalIdentifier"), nameof(ex.ParamName));
            Assert.That(ex.Message,
                        Does.Contain(nationalIdentifier ?? string.Empty),
                        nameof(ex.Message));
        }