Heb 4:15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.
That's right.
If Jesus couldn't sin, how, exactly, was he tested?
Cool i don't mind giving a reason for what i believe. It is inherently a semamtical, subtle argument but hinges on the deity and glory of our Lord.
In Greek there is only one word, that can either mean tested or tempted in English. As English language has evolved it makes a distinction that Greek doesn't, and carries a connotation of arousing sin nascent in one's heart when one is 'tempted' ((see James 1:12-16)) -
that word in Hebrews 4:15 identically literally translates as 'tested' with the correct connotation that there is no sin in the heart or flesh of the Son of God to be aroused.
Therefore how was He tested? As a lamb or red heifer for sacrifice is tested: in every detail to see if any fault, even the slightest blemish, could be found.
Satan tested Him in the wilderness looking for a way to tempt Him, and to find a way to snare Him. The pharisees, sadducees and herodians constantly tested Him first to see if He really was the Messiah and then to see how they could find a way to trap, condemn and kill Him for His words and actions.
In every way we are tested, He was tested and tested still. But He was tested and found perfect, while we are tested and found to have sin in our hearts, our flesh and our words and deeds.
I have the impeccable, faultless, unfailing view of Christ. That He is very God of very God and very man of very man - that that humanity is spotless, perfect, unfallen humanity.
That He is at all times God, never not God, omniscient, omnipotent and always good. That His humanity does not take His deity away. That He and the Father are One God so that when He speaks of and to the Father He does so for our benefit, when He asks a question He knows the answer so He is asking for our benefit, and that while this view makes many things in scripture that superficially seem explicable by stripping Him of deity into profound mysteries, that this profundity is God's purpose, and that it ultimately proves scripture is scripture, that it all glorifies Him, testifies of Him, ans is complex beyond human understanding - that it can only be comprehended by the Spirit of God revealing it and that it cannot possibly have been composed by mere mortal men.
I find that the best way to arrive at right doctrine is to always take the view that glorifies Christ above any view that diminishes Him.