How do you discern between a false prophet and a true prophet? In the Bible it says to beware of false prophets but does not say on how and what to look for either way? Is there any kind of test for this?
Deut 18:20-22 is the classic example from the old testament
20 But the prophet who presumes to speak a word in My name, which I have not commanded him to speak, or who speaks in the name of other gods, that prophet shall die.’ 21 And if you say in your heart, ‘How shall we know the word which the Lord has not spoken?’— 22 when a prophet speaks in the name of the Lord, if the thing does not happen or come to pass, that is the thing which the Lord has not spoken; the prophet has spoken it presumptuously; you shall not be afraid of him. (NKJV)
There are also some examples from the new testament. One such from the Lord Jesus Christ
Then many false prophets will rise up and deceive many. (Matt 24:11)
Jesus says the false prophets will be deceivers. Well, the opposite of deception is truth, Jesus also said some things about the truth.
Sanctify[i] them by Your truth. Your word is truth. (John 17:17).
speaking contrary too the Word of God is a great indicator that they are not in line with the truth, but rather are decievers or "False Prophets".
In addition, Jude speaks of these false teachers.
Beloved, while I was very diligent to write to you concerning our common salvation, I found it necessary to write to you exhorting you to contend earnestly for the faith which was once for all delivered to the saints. 4 For certain men have crept in unnoticed, who long ago were marked out for this condemnation, ungodly men, who turn the grace of our God into lewdness and deny the only Lord [b]God and our Lord Jesus Christ.
Notice Jude says the faith has been "Once for all delivered". We are not awaiting any major new revelations from a prophet. Also he talks about "who turn the grace of God into lewdness". If there message promotes lawlessness or sin in any way, contrary to what has been clearly taught in the Bible, that is a bad sign also.
In addition, the 2nd chapter of 2 Peter is all about false teachers, and would be a good resource for study also.
In conclusion, Paul warns against any "new gospels"
But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be [b]accursed. 9 As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed.(galatians 1:6-8).
So the marks of a true prophet would be, speaking things that line up with God's word and promoting godliness.
Marks of a false prophet would be, new and strange teachings that don't line up with the bible, promoting ungodliness, or any type of prophecy that does not come true.