Revelation 2:2b; Thou Tried Them
Revelation 2:2 … and how thou canst not bear them which are evil: and thou hast tried them which say they are apostles, and are not, and hast found them liars:
The Church at Ephesus had spiritual discernment, able to tell good from evil, true from the false. You may say, they took full heed to Paul’s advice to them when Paul left them in Acts 20 after 3 years of ministry.
Acts 20:28-31 Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood. 29For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock. 30Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them. 31Therefore watch, and remember, that by the space of three years I ceased not to warn every one night and day with tears.
They had the best of teaching. The Apostle Paul himself taught them.