MsTest- ExpectedException fails in base test class, testInitialize

I have a base test calss with a testInitialize method which invokes the unit method I want to test.

In one of the tests I am expecting an exception but since the test initialize method is invoking the unit of execution the exception is thrown and I feel that it never reaches my child classes test method to be confirmed and therefor my test fails.

base test class:

public abstract class EdinburghZoneToCmsZoneMapperTestBase
    {
        protected ZoneCmsBlob _zoneCmsBlob { get; private set; }
        protected ZoneGeoJsonFeatureProperties _zoneFeatureProperties;

        [TestInitialize]
        public void BaseInitialize()
        {            
            _zoneCmsBlob = EdinburghZoneToCmsZoneMapper.Map(MakeZone());
        }

        protected virtual ZoneGeoJsonFeatureProperties MakeZone()
        {
            return new ZoneGeoJsonFeatureProperties
            {
                Name = "1"              
            };
        }
    }

child test class:

[TestClass]
    public class WhenZoneIdIsEmpty: EdinburghZoneToCmsZoneMapperTestBase
    {
        protected override ZoneGeoJsonFeatureProperties MakeZone()
        {
            return new ZoneGeoJsonFeatureProperties
            {
                Name = string.Empty
            };
        }


        [TestMethod]
        [ExpectedException(typeof(ArgumentException))]
        public void ThrowsException()
        {
            Assert.IsTrue(string.IsNullOrWhiteSpace(_zoneFeatureProperties.Name));
        }
    }

system under test:

 public static class EdinburghZoneToCmsZoneMapper
    {
        public static ZoneCmsBlob Map(ZoneGeoJsonFeatureProperties zoneFeature)
        {
            if (string.IsNullOrWhiteSpace(zoneFeature.Name))
                throw new ArgumentException("Zone name cannot be empty");

            throw new NotImplementedException();
        }
    }