Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test! I hope you will find out that we have not failed the test. But we pray to God that you may not do wrong—not that we may appear to have met the test, but that you may do what is right, though we may seem to have failed. (2 Corinthians 13:5-7, ESV)
Paul does not specify what the “test” is to know whether you are saved. …..Paul himself did not supply us with the “test” but only a challenge to take the test. I think there is good reason for this. One who is willing to accept Paul’s challenge and “take the test” is reminded of what constitutes being “in the faith” or “out of the faith.” Paul speaks of those who are “in the faith” as those of whom he can say, “Christ is in you” (verse 5).
The problem at Corinth is that some find the gospel Paul preaches (“Christ crucified”—1 Corinthians 1:23) too simplistic and not very appealing. Some came with a new “gospel”, and at least some Corinthians did not even recognize the switch that had occurred (2 Corinthians 11:3-4). When the “gospel” becomes “Christ or …” or “Christ and ….,” it is not the gospel Paul preaches, but a “gospel” which keeps us from ever knowing for certain that we are “in the faith.”
This is because the new “gospel” requires something of us.
The gospel Paul preaches is Christ only. Apart from Christ, we are sinners, deserving of God’s eternal wrath (hell). In Christ, we are dead to sin and its penalty, alive to righteousness, awaiting our eternal hope of heaven. When you test yourself, does your salvation depend upon you, upon your status, your performance, your works, or upon Christ? If you recognize that apart from Christ, you are “dead in your trespasses and sins,” and that you are saved by faith—not by your good works—and that you are now“in Christ” (see Ephesians 2:1-10), then you know you are saved. Nothing can change this, for your salvation depends only on Christ and what He has already accomplished on the cross of Calvary and in His resurrection from the dead.
Knowing God through His Word ... Day by Day 
Reblogged this on My Delight and My Counsellors.
I agree that you can only become saved through Christ. However your works after you become saved will show whether you are truly saved, whether you truly know Christ and if Christ truly knows you (Matthew 7:21-23).