I don’t know the Catholic version… why did the angles need to be tested

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Can you please share a link to a good source as I would like to know?
I’m not sure we can call it a “test” in our sense of the term. Perhaps better to call it a “choice”. If one creates a creature with free will, that creature may decide for or against its creator, otherwise it would not have free will. It’s simply part of having free will.
I don’t think that’s too hard to understand. We all want love to be voluntary toward ourselves. Coerced regard or even love is not worth a great deal.
If, as Christians believe, God is infinite in all affirmative attributes of which we know, then the angels could not have known God “as He is” because no limited creature can ever do that, no matter how wise or how long he is at it. There is, therefore, always a certain degree of mystery to God, no matter what.
But angels certainly knew themselves, and they knew what they knew of God. If, as Christians believe, angels are of such magnificent nature that if we somehow perceived one as it is, we would immediately think it was God and resist thinking otherwise.
So, if humans, being the meat-sacks we are, who cannot even deduce what is two feet in the ground below us accurately, let alone what constitutes a quark, can opt for the kind of vanity we sometimes see or even experience in ourselves, how much greater the temptation of a creature which, for all we know, could logically deduce not only that the “big bang” was going to take place (when, we don’t know) but that it was the result of the collision of two “membranes” (if that’s what it was) and could instantly reason back to what was there before the “big bang” which (I understand) will probably forever elude human knowledge.
Remember the Faustian bargain? Faust volunteered to his own damnation if ever he said to a moment “stay, you are so beautiful”. We read Faust, and while that sentiment seems extreme, we do understand it. And we understand why it’s damning to say it.
And perhaps the fallen angels simply decided (with more clarity than we will ever have this side of death) to say to the moment “stay I AM so beautiful”. One remembers that the name of the archangel Michael means “who is like God”. LIKE God, magnificent beyond our understanding, but short of it. Indeed, even we do that sort of thing, as ridiculous as we are in doing it. And when we regard ourselves as beautiful (in the widest sense) we can get even murderously resentful of any suggestion that we are not, particularly when we know we are not.
Dependent, forever dependent on the well-spring of everything we are, even though the dependency meant ever-enriched wisdom and other attributes. Powerfully grateful always, for that enrichement. And service. We understand they were to serve in some manner, though we don’t know what it was. Perhaps it was different for every one.
Hard to fully understand saying to the moment and the status “Stay you are/I am so beautiful”, expecially in the context of huge wisdom. But it’s not entirely incomprehensible, even to us.