'Attesting' in the Bible

The Pharisees came out and began to argue [contentiously and debate] with Him, demanding from Him a sign from heaven, to test Him [because of their unbelief].

These signs will accompany those who have believed: in My name they will cast out demons, they will speak in new tongues;

And they went out and preached everywhere, while the Lord was working with them and confirming the word by the signs that followed.]