Reset class map for unit testing

BsonClassMapHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using MongoDB.Bson.Serialization;

namespace CQRS.Tests.DomainTests
{
    public static class BsonClassMapHelper
    {
        public static void Unregister<T>()
        {
            var classType = typeof(T);
            GetClassMap().Remove(classType);
        }

        static Dictionary<Type, BsonClassMap> GetClassMap()
        {
            var cm = BsonClassMap.GetRegisteredClassMaps().First();
            var fi = typeof(BsonClassMap).GetField("__classMaps", BindingFlags.Static | BindingFlags.NonPublic);
            var classMaps = (Dictionary<Type, BsonClassMap>)fi.GetValue(cm);
            return classMaps;
        }

        public static void Clear()
        {
            GetClassMap().Clear();
        }
    }
}