Reset class map for unit testing

BsonClassMapHelper.cs

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

namespace Mongo.Gist
{
    /// <summary>
    /// Class BsonClassMapHelper.
    /// </summary>
    public static class BsonClassMapHelper
    {
        /// <summary>
        /// Unregister a type.
        /// </summary>
        /// <typeparam name="T">Type to unregister.</typeparam>
        public static void Unregister<T>()
        {
            var classType = typeof(T);
            GetClassMap(classType).Remove(classType);
        }

        /// <summary>
        /// Gets the mapping dictionary.
        /// </summary>
        /// <param name="classType"></param>
        /// <returns></returns>
        private static Dictionary<Type, BsonClassMap> GetClassMap(Type classType)
        {
            var classMap = BsonClassMap.LookupClassMap(classType);
            var fieldInfo = typeof(BsonClassMap).GetField("__classMaps", BindingFlags.Static | BindingFlags.NonPublic);

            return (Dictionary<Type, BsonClassMap>)fieldInfo.GetValue(classMap);
        }
    }
}