Sanity check C# unit tests for ironclad cpymarshaltest throwing an ERROR

CPyMarshalTest.cs

using System;
using System.Runtime.InteropServices;
using System.Collections.Generic;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Ironclad.Structs;

namespace Ironclad.Tests
{
    [TestClass]
    public class CPyMarshalTest32
    {

        [TestMethod]
        public void WriteDoubleTest()
        {
            var data = Marshal.AllocHGlobal(CPyMarshal.DoubleSize);
            
            CPyMarshal.WriteDouble(data, 2.2e22);
            var doubleStruct = (DoubleStruct)Marshal.PtrToStructure(data, typeof(DoubleStruct));
            Assert.AreEqual(doubleStruct.value, 2.2e22);

            Marshal.FreeHGlobal(data);
        }

        [TestMethod]
        public void WriteDoubleFieldTest()
        {
            var data = Marshal.AllocHGlobal(Marshal.SizeOf(typeof (PyFloatObject)));
            CPyMarshal.Zero(data, Marshal.SizeOf(typeof(PyFloatObject)));

            CPyMarshal.WriteDoubleField(data, typeof(PyFloatObject), "ob_fval", 7.6e-5);
            var dataStruct = (PyFloatObject) Marshal.PtrToStructure(data, typeof (PyFloatObject));
            Assert.AreEqual(dataStruct.ob_fval, 7.6e-5);

            Marshal.FreeHGlobal(data);
        }

        [TestMethod]
        public void WriteIntFieldTest()
        {
            var data = Marshal.AllocHGlobal(Marshal.SizeOf(typeof (PyIntObject)));
            CPyMarshal.Zero(data, Marshal.SizeOf(typeof (PyIntObject)));

            var values = new List<Int32> {Int32.MaxValue, Int32.MinValue};
            foreach(var value in values)
            {
                CPyMarshal.WriteIntField(data, typeof(PyIntObject), "ob_ival", value);
                var dataStruct = (PyIntObject) Marshal.PtrToStructure(data, typeof (PyIntObject));
                Assert.AreEqual(dataStruct.ob_ival, value, "failed to write");
            }

            Marshal.FreeHGlobal(data);
        }

        [TestMethod]
        public void WritePtrFieldTest()
        {
            var data = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(PyObject)));
            CPyMarshal.Zero(data, Marshal.SizeOf(typeof(PyObject)));

            CPyMarshal.WritePtrField(data, typeof(PyObject), "ob_type", new IntPtr(12345));
            var dataStruct = (PyObject) Marshal.PtrToStructure(data, typeof (PyObject));
            Assert.AreEqual(dataStruct.ob_type, new IntPtr(12345), "failed to write");

            Marshal.FreeHGlobal(data);
        }

        [TestMethod]
        public void WriteUIntFieldTest()
        {
            var data = Marshal.AllocHGlobal(Marshal.SizeOf(typeof (PyTypeObject)));
            CPyMarshal.Zero(data, Marshal.SizeOf(typeof(PyTypeObject)));

            var values = new List<UInt32> {UInt32.MaxValue, UInt32.MinValue};
            foreach (var value in values)
            {
                CPyMarshal.WriteUIntField(data, typeof(PyTypeObject), "tp_version_tag", value);
                var dataStruct = (PyTypeObject) Marshal.PtrToStructure(data, typeof (PyTypeObject));
                Assert.AreEqual(dataStruct.tp_version_tag, value, "failed to write");
            }

            Marshal.FreeHGlobal(data);
        }
    }
}