Workaround completely test-unfriendly sql error classes

SqlExceptionMocker.cs

using System.Data.SqlClient;
using System.Reflection;

namespace HorribleThingsInHere
{
    /// <summary>
    /// Workaround completely test-unfriendly sql error classes.
    /// Copy-paste from http://stackoverflow.com/a/1387030/10245
    /// Adjusted with updates in comments
    /// </summary>
    class SqlExceptionMocker
    {
        private static T Construct<T>(int ctorIndex, params object[] p)
        {
            var ctors = typeof (T).GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance);
            var ctor = ctors[ctorIndex];
            return (T)ctor.Invoke(p);
        }

        public static SqlException MakeSqlException(int errorNumber)
        {

            var collection = Construct<SqlErrorCollection>(0);
            var error = Construct<SqlError>(1, errorNumber, (byte) 2, (byte) 3, "server name", "This is a Mock-SqlException", "proc", 100);

            typeof (SqlErrorCollection)
                .GetMethod("Add", BindingFlags.NonPublic | BindingFlags.Instance)
                .Invoke(collection, new object[] {error});


            var e = typeof (SqlException)
                .GetMethod("CreateException", BindingFlags.NonPublic | BindingFlags.Static, null, CallingConventions.ExplicitThis, new[] {typeof (SqlErrorCollection), typeof (string)}, new ParameterModifier[] {})
                .Invoke(null, new object[] {collection, "7.0.0"}) as SqlException;

            return e;
        }
    }
}

Check out @martinjw's fork for a copy and paste ready source: https://gist.github.com/martinjw/668700c8d199312dad7d

On .NET 4.7.2 I had to use this line:
var error = Construct<SqlError>(errorNumber, (byte) 2, (byte) 3, "server name", "This is a Mock-SqlException", "proc", 100, 0u);

There seems to be a new UInt32 parameter at the end.