How do I know if a wolf in sheep’s clothing is in the midst?

I have had on several occasions been told a person is a deceiver. The first time the Lord told me this, I had no idea what the Lord was telling me. The person appeared to be a Christian, walking with the Lord. They even worked in a Christian school. Yet, “deceiver, deceiver was being declared in my spirit.

What is a deceiver? Jesus tells us in His word:

“For many deceivers have gone out into the world who do not confess Jesus Christ as coming in the flesh. This is a deceiver and an antichrist.” 2 John 1:7

A deceiver appears to be a Christian, yet they do not confess Jesus has come in the flesh and the fruit being produced is not of the Lord. 

“Watch out for false prophets. They come to you in sheep’s clothing, but inwardly they are ferocious wolves. By their fruit you will recognize them. Do people pick grapes from thorn bushes, or figs from thistles?” Mathew 7:15-16,

We are warned not to believe every spirit, “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.” 1 John 4:1