Because many false prophets have gone out, what does 1 John 4:1 tell believers to do?

Answer: Test the spirits

"Do not believe every spirit, but test the spirits to see whether they are from God. For many false prophets have gone out."

“Beloved, do not believe every spirit, but test the spirits to see whether they are from God. For many false prophets have gone out into the world.”— 1 John 4:1 (BSB)