What is the test Paul is speaking of in 2 Corinthians 13:5?

Please explain the "test" mentioned in 2 Corinthians 13:5?

Paul’s comments in 2 Corinthians come in the context of a larger discussion:

2Cor. 13:1 This is the third time I am coming to you. every fact is to be confirmed by the testimony of two or three witnesses.
2Cor. 13:2 I have previously said when present the second time, and though now absent I say in advance to those who have sinned in the past and to all the rest as well, that if I come again I will not spare anyone,
2Cor. 13:3 since you are seeking for proof of the Christ who speaks in me, and who is not weak toward you, but mighty in you.
2Cor. 13:4 For indeed He was crucified because of weakness, yet He lives because of the power of God. For we also are weak in Him, yet we will live with Him because of the power of God directed toward you.
2Cor. 13:5 Test yourselves to see if you are in the faith; examine yourselves! Or do you not recognize this about yourselves, that Jesus Christ is in you — unless indeed you fail the test?
2Cor. 13:6 But I trust that you will realize that we ourselves do not fail the test.
2Cor. 13:7 Now we pray to God that you do no wrong; not that we ourselves may appear approved, but that you may do what is right, even though we may appear unapproved.

In v.3 Paul says that the church in Corinth was seeking for a “proof” or test that Paul was truly speaking for Christ as an apostle, to which Paul replied that his audience should apply the same test to themselves. Paul is saying that before they judge him, they should judge themselves. Before they criticize him for not following Christ properly or not speaking for Christ accurately, they should examine themselves to see if they know and live the truth properly.

Paul issued this challenge having already defended himself against numerous accusations levied against him by his critics in the city in the prior chapters of the letter. Paul had patiently explained his teaching and motives against false accusations, so now he turns the tables on the church and asks them to examine their own behaviors and motives to see if they are living in keeping with Christ’s will.

Therefore, Paul's test refers to the question of whether a Christian is operating in the faith, in Christ’s will and according to His word. His critics were those who failed this test since they were carnal Christians operating outside Christ’s will. Since they opposed Paul, in whom Christ spoke, they were failing the test they placed on Paul himself.