Off the top of my head:
1. The test of resilience.
1 John 2:18-19 KJV
18. Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time.
19. They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
You are either the spirit of God or the spirit of the anti-christ. There are no other spirits you can be. If you keep coming back, you are of God.
2. The test of heresy.
1 Corinthians 11:19 KJV
19. For there must be also heresies among you, that they which are approved may be made manifest among you.
If you are true, you will remain with the truth. One who is not, will wander off into "damnable heresies."
3. The test of confession.
1 Corinthians 12:3 KJV
3. Wherefore I give you to understand, that no man speaking by the Spirit of God calleth Jesus accursed: and that no man can say that Jesus is the Lord, but by the Holy Ghost.
Paul here is talking about manifestation of the spirit.
4. The test of spiritual fruit.
1 John 3:9-10 KJV
9. Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.
10. In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother.
The part of the believer that is born of God is our spirit. If you are saved your spirit is born of God, and you CANNOT sin from that spirit, because it is born of God.
5. The Abba test.
Romans 8:15-16 KJV
15. For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father.
16. The Spirit itself beareth witness with our spirit, that we are the children of God:
6. The inner witness test.
1 John 5:10 KJV
10. He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.
I think the believer cannot talk himself out of it, and nobody can talk the believer out of it. You may have mental doubt and reservations, but in your spirit, you are convinced.