No, I believe that God will enlighten anyonenot just Mormonswho asks him in faith. That is what Jesus taught:
Ask, and it shall be given you; seek and ye shall find; knock, and it shall be opened unto you: For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened. (Matthew 7:78)
Is personal revelation from the Holy Spirit subjective? Perhaps. But so are faith, hope, and charity, which are essential to a Christian life.
So what test do you use to determine that you are not being duped by the devil or yourself? Quite frankly, all thoughts that enter into our mind are not God's Spirit enlightening us...
Regards