example_of_test_factory_with_builder_pattern.cs

[TestFixture]
public class IdVerificationTests
{
    [Test,TestCaseSource(typeof(IdVerificationTestFactory), nameof(IdVerificationTestFactory.ItShouldVerifyTheseCustomers))]
    public void Should_verify_customer_identity(Customer customer, Country country,
        bool responseCode)
    {
        given_an_idverification_request(customer, country);
        when_idverification_is_requested();
        then_it_should_have_verified_customer(responseCode);
    }
}

public class IdVerificationTestFactory
{
    public static IEnumerable ItShouldVerifyTheseCustomers
    {
        get
        {
            foreach (var customer in CustomerRepository.GetAllVerifiableCustomers())
            {
                var country = CountryRepository.GetCountry(customer.AddressAlpha2IsoCountryCode);
                yield return new TestCaseBuilder()
                    .ItShouldReturnTrue()
                    .WithCustomer(customer)
                    .FromCountry(country)
                    .Build();
            }
        }
    }
}

public class TestCaseBuilder
{
    private Customer _customer;
    private Country _country;
    private string _testName;
    private bool _expectedValue;

    public TestCaseBuilder ItShouldReturnTrue()
    {
        _expectedValue = true;
        _testName = "It_should_return_true";
        return this;
    }

    public TestCaseBuilder ItShouldReturnFalse()
    {
        _expectedValue = false;
        _testName = "It_should_return_false";
        return this;
    }

    public TestCaseBuilder WithCustomer(Customer customer)
    {
        _customer = customer;
        _testName += "_for_customer_" + customer.FirstName;
        return this;
    }

    public TestCaseBuilder FromCountry(Country country)
    {
        _country = country;
        _testName += "_for_country_" + country.Alpha2IsoCountryCode;
        return this;
    }

    public TestCaseData Build()
    {
        return new TestCaseData(_customer, _country, _expectedValue).SetName(_testName);
    }
}