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Who cares about Domain Rules?

, 20 Nov 2006 MIT
With this article, I am evolving a domain problem towards the best possible solution.
domainrules_src.zip
BusinessRules
0 - Procedural_Way
0 - Procedural_Way.smp
ProceduralWay.cd
Tests
1 - Evolution One
1 - Evolution One.smp
EvolutionOne.cd
Tests
2 - Evolution Two
2 - Evolution Two.smp
EvolutionTwo.cd
Tests
3 - Evolution Three
3 - Evolution Three.smp
EvolutionThree.cd
IncomeTaxEngine.cd
Tests
4 - Evolution Four
4 - Evolution Four.smp
EvolutionFour.cd
Tests
5 - Evolution Five
5 - Evolution Five.smp
EvolutionFive.cd
TaxBandGenerator.cd
Tests
bin
Debug
BusinessRules.dll
BusinessRules.dll.lastcodeanalysissucceeded
NMock2.dll
BusinessRules.csproj.user
obj
Debug
BusinessRules.dll
TempPE
Properties
Tools
NMock2.dll
nunit.framework.dll
using NUnit.Framework;

namespace BusinessRules.Procedural_Way.Tests
{
    [TestFixture]
    public class InvestorFixture
    {
        [Test]
        public void TaxRateCalculatedCorrectlyForUS()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the US culture name.
            investor.CurrentCultureName = "en-US";

            // Validate the income tax engine for USA works as expected

            Assert.AreEqual(0.10, investor.TaxRate);
            investor.Income = 1500.00;
            Assert.AreEqual(0.10, investor.TaxRate);
            investor.Income = 7550.99;
            Assert.AreEqual(0.10, investor.TaxRate);

            investor.Income = 7551.00;
            Assert.AreEqual(0.15, investor.TaxRate);
            investor.Income = 28000.00;
            Assert.AreEqual(0.15, investor.TaxRate);
            investor.Income = 30650.99;
            Assert.AreEqual(0.15, investor.TaxRate);

            investor.Income = 30651.00;
            Assert.AreEqual(0.25, investor.TaxRate);
            investor.Income = 65000.00;
            Assert.AreEqual(0.25, investor.TaxRate);
            investor.Income = 74200.99;
            Assert.AreEqual(0.25, investor.TaxRate);

            investor.Income = 74201.00;
            Assert.AreEqual(0.28, investor.TaxRate);
            investor.Income = 84526.00;
            Assert.AreEqual(0.28, investor.TaxRate);
            investor.Income = 154800.99;
            Assert.AreEqual(0.28, investor.TaxRate);

            investor.Income = 154801.00;
            Assert.AreEqual(0.33, investor.TaxRate);
            investor.Income = 205456.44;
            Assert.AreEqual(0.33, investor.TaxRate);
            investor.Income = 336550.99;
            Assert.AreEqual(0.33, investor.TaxRate);

            investor.Income = 336551.00;
            Assert.AreEqual(0.35, investor.TaxRate);
            investor.Income = 536551.00;
            Assert.AreEqual(0.35, investor.TaxRate);
            investor.Income = double.MaxValue - 0.01;
            Assert.AreEqual(0.35, investor.TaxRate);
        }

        [Test]
        public void TaxLiabilityCalculatedCorrectlyForUS()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the US culture name.
            investor.CurrentCultureName = "en-US";

            // Validate the income tax engine for USA works as expected

            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 1500.00;
            Assert.AreEqual(150.00, investor.TaxLiability, 2.0);
            investor.Income = 7550.99;
            Assert.AreEqual(755.10, investor.TaxLiability, 2.0);

            investor.Income = 7551.00;
            Assert.AreEqual(755.10, investor.TaxLiability, 2.0);
            investor.Income = 28000.00;
            Assert.AreEqual(3822.45, investor.TaxLiability, 2.0);
            investor.Income = 30650.99;
            Assert.AreEqual(4220.10, investor.TaxLiability, 2.0);

            investor.Income = 30651.00;
            Assert.AreEqual(4220.10, investor.TaxLiability, 2.0);
            investor.Income = 65000.00;
            Assert.AreEqual(12807.35, investor.TaxLiability, 2.0);
            investor.Income = 74200.99;
            Assert.AreEqual(15107.60, investor.TaxLiability, 2.0);

            investor.Income = 74201.00;
            Assert.AreEqual(15107.60, investor.TaxLiability, 2.0);
            investor.Income = 84526.00;
            Assert.AreEqual(17998.60, investor.TaxLiability, 2.0);
            investor.Income = 154800.99;
            Assert.AreEqual(37675.60, investor.TaxLiability, 2.0);

            investor.Income = 154801.00;
            Assert.AreEqual(37675.60, investor.TaxLiability, 2.0);
            investor.Income = 205456.44;
            Assert.AreEqual(54391.89, investor.TaxLiability, 2.0);
            investor.Income = 336550.99;
            Assert.AreEqual(97653.09, investor.TaxLiability, 2.0);

            investor.Income = 336551.00;
            Assert.AreEqual(97653.09, investor.TaxLiability, 2.0);
            investor.Income = 536551.00;
            Assert.AreEqual(167653.09, investor.TaxLiability, 2.0);
            investor.Income = double.MaxValue - 0.01;
            Assert.AreEqual(6.2919259720181043E+307, investor.TaxLiability, 2.0);
        }

        [Test]
        public void TaxRateCalculatedCorrectlyForAustralia()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the Australian culture name.
            investor.CurrentCultureName = "en-AU";

            // Validate the income tax engine for Australian works as expected

            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 1500.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 6000.99;
            Assert.AreEqual(0.0, investor.TaxRate);

            investor.Income = 6001.00;
            Assert.AreEqual(0.15, investor.TaxRate);
            investor.Income = 22258.32;
            Assert.AreEqual(0.15, investor.TaxRate);
            investor.Income = 25000.99;
            Assert.AreEqual(0.15, investor.TaxRate);

            investor.Income = 25001.00;
            Assert.AreEqual(0.30, investor.TaxRate);
            investor.Income = 65000.00;
            Assert.AreEqual(0.30, investor.TaxRate);
            investor.Income = 75000.99;
            Assert.AreEqual(0.30, investor.TaxRate);

            investor.Income = 75001.00;
            Assert.AreEqual(0.40, investor.TaxRate);
            investor.Income = 84526.00;
            Assert.AreEqual(0.40, investor.TaxRate);
            investor.Income = 150000.99;
            Assert.AreEqual(0.40, investor.TaxRate);

            investor.Income = 150001.00;
            Assert.AreEqual(0.45, investor.TaxRate);
            investor.Income = 205456.44;
            Assert.AreEqual(0.45, investor.TaxRate);
            investor.Income = double.MaxValue - 0.01;
            Assert.AreEqual(0.45, investor.TaxRate);
        }

        [Test]
        public void TaxLiabilityCalculatedCorrectlyForAustralia()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the Australian culture name.
            investor.CurrentCultureName = "en-AU";

            // Validate the income tax engine for Australian works as expected

            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 1500.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 6000.99;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);

            investor.Income = 6001.00;
            Assert.AreEqual(0.15, investor.TaxLiability, 2.0);
            investor.Income = 22258.32;
            Assert.AreEqual(2438.60, investor.TaxLiability, 2.0);
            investor.Income = 25000.99;
            Assert.AreEqual(2850.00, investor.TaxLiability, 2.0);

            investor.Income = 25001.00;
            Assert.AreEqual(2850.00, investor.TaxLiability, 2.0);
            investor.Income = 65000.00;
            Assert.AreEqual(14849.70, investor.TaxLiability, 2.0);
            investor.Income = 75000.99;
            Assert.AreEqual(17850.00, investor.TaxLiability, 2.0);

            investor.Income = 75001.00;
            Assert.AreEqual(17850.00, investor.TaxLiability, 2.0);
            investor.Income = 84526.00;
            Assert.AreEqual(21660.00, investor.TaxLiability, 2.0);
            investor.Income = 150000.99;
            Assert.AreEqual(47850.00, investor.TaxLiability, 2.0);

            investor.Income = 150001.00;
            Assert.AreEqual(47850.00, investor.TaxLiability, 2.0);
            investor.Income = 205456.44;
            Assert.AreEqual(72804.94, investor.TaxLiability, 2.0);
            investor.Income = double.MaxValue - 0.01;
            Assert.AreEqual(8.0896191068804208E+307, investor.TaxLiability, 2.0);
        }

        [Test]
        public void TaxRateCalculatedCorrectlyForNewZealand()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the New Zealand culture name.
            investor.CurrentCultureName = "en-NZ";

            // Validate the income tax engine works as expected

            Assert.AreEqual(0.195, investor.TaxRate);
            investor.Income = 9500.00;
            Assert.AreEqual(0.195, investor.TaxRate);
            investor.Income = 19500.00;
            Assert.AreEqual(0.195, investor.TaxRate);
            investor.Income = 19500.99;
            Assert.AreEqual(0.195, investor.TaxRate);

            investor.Income = 19501.00;
            Assert.AreEqual(0.33, investor.TaxRate);
            investor.Income = 28000.00;
            Assert.AreEqual(0.33, investor.TaxRate);
            investor.Income = 60000.00;
            Assert.AreEqual(0.33, investor.TaxRate);
            investor.Income = 60000.99;
            Assert.AreEqual(0.33, investor.TaxRate);

            investor.Income = 60001.00;
            Assert.AreEqual(0.39, investor.TaxRate);
            investor.Income = 65000.00;
            Assert.AreEqual(0.39, investor.TaxRate);
            investor.Income = 999999999.00;
            Assert.AreEqual(0.39, investor.TaxRate);
        }

        [Test]
        public void TaxLiabilityCalculatedCorrectlyForNewZealand()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the New Zealand culture name.
            investor.CurrentCultureName = "en-NZ";

            // Validate the income tax engine works as expected

            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 9500.00;
            Assert.AreEqual(1852.50, investor.TaxLiability, 2.0);
            investor.Income = 19500.00;
            Assert.AreEqual(3802.50, investor.TaxLiability, 2.0);
            investor.Income = 19500.99;
            Assert.AreEqual(3802.69, investor.TaxLiability, 2.0);

            investor.Income = 19501.00;
            Assert.AreEqual(3802.70, investor.TaxLiability, 2.0);
            investor.Income = 28000.00;
            Assert.AreEqual(6607.36, investor.TaxLiability, 2.0);
            investor.Income = 60000.00;
            Assert.AreEqual(17167.36, investor.TaxLiability, 2.0);
            investor.Income = 60000.99;
            Assert.AreEqual(17167.69, investor.TaxLiability, 2.0);

            investor.Income = 60001.00;
            Assert.AreEqual(17167.69, investor.TaxLiability, 2.0);
            investor.Income = 65000.00;
            Assert.AreEqual(19117.30, investor.TaxLiability, 2.0);
            investor.Income = 999999999.00;
            Assert.AreEqual(389993766.91, investor.TaxLiability, 2.0);
            investor.Income = double.MaxValue - 0.01;
            Assert.AreEqual(7.0110032259630313E+307, investor.TaxLiability, 2.0);
        }

        [Test]
        public void TaxRateCalculatedCorrectlyForNonExceptionalBehavior()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the un-supported culture name.
            investor.CurrentCultureName = "en-ZA";

            // Validate the income tax engine for Non-Exceptional behavior works as expected

            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 9500.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 19500.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 19500.99;
            Assert.AreEqual(0.0, investor.TaxRate);

            investor.Income = 19501.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 28000.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 60000.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 60000.99;
            Assert.AreEqual(0.0, investor.TaxRate);

            investor.Income = 60001.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 65000.00;
            Assert.AreEqual(0.0, investor.TaxRate);
            investor.Income = 999999999.00;
            Assert.AreEqual(0.0, investor.TaxRate);
        }

        [Test]
        public void TaxLiabilityCalculatedCorrectlyForNonExceptionalBehavior()
        {
            // Create the instance of the investor
            Investor investor = new Investor(0.0);
            // Set the CurrentCultureName to the un-supported culture name.
            investor.CurrentCultureName = "en-ZA";

            // Validate the income tax engine for Non-Exceptional behavior works as expected

            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 9500.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 19500.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 19500.99;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);

            investor.Income = 19501.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 28000.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 60000.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 60000.99;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);

            investor.Income = 60001.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 65000.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = 999999999.00;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
            investor.Income = double.MaxValue - 0.01;
            Assert.AreEqual(0.0, investor.TaxLiability, 2.0);
        }
    }
}

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About the Author

Maruis Marais
Web Developer
New Zealand New Zealand
No Biography provided

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