Instrument with property access

winning.cs

    public class Instrument : DynamicObject
    {
        public int FinancialInstrumentId { get; private set; }
        public string SpecialType { get; private set; }

        public Instrument(int finId,string specialType)
        {
            FinancialInstrumentId = finId;
            SpecialType = specialType;
        }


        public bool Is(string specialType)
        {
            return SpecialType.Contains(specialType);
        }

        public override bool TryGetMember(GetMemberBinder binder,
                                  out object result)
        {
            if (!binder.Name.StartsWith("Is")) throw new ArgumentException("Property doesn't exist");
            result = SpecialType.Contains(binder.Name.Substring(2));
            return true;
        }
    }

    [TestFixture]
    public class InstrumentTests
    {

        [Test]
        public void TestIsMethodWithCorrectSpecialType()
        {
            dynamic i = new Instrument(1,"FXBarrier");
            var result = i.Is("FXBarrier");
            Assert.IsTrue(result);
        }

        [Test]
        public void TestIsMethodWithLongCorrectSpecialType()
        {
            dynamic i = new Instrument(3, "100FXBarrierOptionNoKO");
            var result = i.Is("FXBarrier");
            Assert.IsTrue(result);
        }

        [Test]
        public void TestIsMethodWithIncorrectSpecialType()
        {
            dynamic i = new Instrument(5, "EuroOption");
            var result = i.Is("FXBarrier");
            Assert.IsFalse(result);
        }

        [Test]
        public void TestIsWithMethodMissingOverrideWithCorrectSpecialType()
        {
            dynamic i = new Instrument(2, "FXBarrier");
            var result = i.IsFXBarrier;
            Assert.IsTrue(result);
        }

        [Test]
        public void TestIsWithPropertyAccessLongCorrectSpecialType()
        {
            dynamic i = new Instrument(3, "100FXBarrierOptionNoKO");
            var result = i.IsFXBarrier;
            Assert.IsTrue(result);
        }

        [Test]
        public void TestIsWithPropertyAccessIncorrectSpecialType()
        {
            dynamic i = new Instrument(6, "EuroOption");
            var result = i.IsFXBarrier;
            Assert.False(result);
        }

        [Test]
        public void TestThrowsExceptionWhenPropertyNotStartingWithIs()
        {
            dynamic i = new Instrument(6, "EuroOption");
            Assert.That(()=>i.EuroOption,Throws.ArgumentException);
        }
    }