Real and False Prophets vs God's Will

In the Old Testament God told the people of Israel how they could identify if a prophet was a real prophet or a false prophet.

 

    And if you say in your heart, 'How may we know the word that the Lord has not spoken?'— when a prophet speaks in the name of the Lord, if the word does not come to pass or come true, that is a word that the Lord has not spoken; the prophet has spoken it presumptuously. You need not be afraid of him. Deuteronomy 18:21-22

 

Seems kind of simplistic, if what is prophesied happens the prophet is a real prophet. If what was prophesied does not happen the prophet is a false prophet.

 

Maybe if we say, as James tells us to say "If the Lord wills, we will live and do this or that" God's will is whatever happens. Maybe it is like prayer. God does not need for us to pray, we need to pray. God knows his will we do not. We must show ourselves we are willing to accept God's will. So whatever our attitude that is what happens. Because we all know God's ultimate will:

 

    "For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. John 3:16  

 

    The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance. 2 Peter 3:9