Thank you brother. I always appreciate biblical wisdom and sound doctrine. I do believe it is wise to test the spirits, and I also believe that the "test" is quite simple and given to us by the Apostle John. In his time, the first century AD, there were already many antichrists and deceivers. From comments in the epistles it seems as though there were even epistles circulated with false authorship attributed to the Apostles.
John wrote:
4 Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world. 2 By this you know the Spirit of God: Every spirit that confesses that Jesus Christ has come in the flesh is of God, 3 and every spirit that does not confess that Jesus Christ has come in the flesh is not of God. And this is the spirit of the Antichrist, which you have heard was coming, and is now already in the world. 1 John 4:1-3
This is not a test of sound doctrine but of a righteous spirit.
It has been my experience that cultists are never willing to confess that Jesus Christ and all that His title means as declared by scripture, has come in the flesh. Mohammed believed that Jesus was born to a woman named Mary, but did not believe that He is the only begotten Son of God, but called Him a prophet. Jehovah's witnesses are willing to call Him a son of God, but not the only begotten Son and equal to the Father. Others call the Lord a created being as well, always making Him less than the person of the Eternal God and Creator in a tabernacle of human flesh.
This site has rules about challenging the salvation of posters, but no born again believer has a problem with making a public confession of their faith in Christ and I find no valid reason for offense at being asked to share the reason for one's faith. On the contrary, those I know personally that are "in christ" are delighted to talk about our beloved Savior. Who doesn't like to talk about those that they love and that love them?
This isn't the same as being duplicative and asking questions just to catch someone in an error, something that the pharisees and scribes did to our Lord. In His grace the Lord did not condemn His detractors though He had no problem with calling out a wrong spirit, but rather, warned them not to blaspheme the Holy Spirit. Even though the Holy Spirit was not given to permanently indwell His disciples before the resurrection, He was still with them and performed great works through them to the glory of our Father through faith in His Son, our Lord and Savior, Jesus the Christ, blessed forever. Amen.