Book of Mormon Promise

The promise in the Book of Mormon, written by Moroni that if a person will read, ponder and pray about the Book of Mormon they will receive a spiritual witness that the book is true. The promise indicates that those who seek this witness need to search with real intent.

3   Behold, I would exhort you that when ye shall read these things, if it be wisdom in God that ye should read them, that ye would remember how merciful the Lord hath been unto the children of men, from the creation of Adam, even down until the time that ye shall receive these things, and ponder it in your hearts.
4   And when ye shall receive these things, I would exhort you that ye would ask God, the eternal Father, in the name of Christ, if these things are not true; ⁵and if ye shall ask with a sincere heart, with real intent, having faith in Christ, [and] he will manifest the truth of it unto you, by the power of the Holy Ghost.
5   And by the power of the Holy Ghost, ye may know the truth of all things.

--Moroni 10.3-5

Superscript denotes alternate versification; all items in brackets are discreptancies among texts.

The problem with this promise is that there's only one possible outcome. If you don't get the special burning feeling that is supposed to be interpreted as an answer in the affirmative, or even if you get what you consider a negative answer, Mormons will simply inform you that you need to try again and pray harder. In their formula there is no valid way for the book to fail the test.