Somebody say: I took the full test score
And I answer: Good for you!
which one is correct in Russian:
"хорошо для тебя"
And also we use "тебе на пользу" in another situation like: eating healthy food is good for you ?
хорошо для тебя in this context is not idiomatic.
I guess in Russian it can be expressed with Поздравляю! or Молодец/Молодчина!
(Тебе) везёт / Везёт (тебе) is suitable in situations where luck is truly a determinant or when there's some degree of jealousy involved.
In the context of physical benefit it's usually phrased as полезно, and тебе полезно when it's beneficial specifically to that person
тебе на пользу is normally coupled with the verb идти and refers to certain vivid signs of the benefit or lack thereof observed in the person after the fact or predicted.
As mentioned above, most common is to use "Поздравляю!", but you can also use "Здорово!" or "Рад за тебя!".
You should be really careful using "Хорошо тебе", which is most literal translation, but implies jealousy and may actually mean you are not happy for this person.
As per last paragraph, most common in this case is word "полезно". E.g. "Заниматься спортом полезно". ("Doing sports is good for you / Doing sports is healthy"). You can also say "
Заниматься спортом Спорт пойдет тебе на пользу" which is a bit more an advice than a neutral statement and implies that you should start doing sports.
The answer depends on whether or not you wanted to use "good for you" as a sarcastic retort, which is how that expression is frequently used nowadays when the speaker has no interest in someone else's happy moment, as in "good for you, but why should I care?"
If you were genuinely happy for that person, you could say "Я рад/рада за тебя!" ("I'm glad(m/f) for you!") or, more neutrally, "Ну и отлично." (roughly "Well, great.") Your second option "Повезло тебе" might work, but implies the high score may not have been well deserved. Баян Купи-ка's answer offers a few other nice options.
If you were going for sarcasm lined with thinly veiled indifference and annoyance, however, a more appropriate reply could be "ну и ладно" (roughly, "well, okay"), or "какой/какая молодец" (roughly, "attaboy/attagirl") with "какой/какая" drawled and overarticulated. Note that being sarcastic in a language you don't speak very well may have disastrous consequences for you and is best avoided altogether (not that it's ever right to be sarcastic even in your native language anyway).
"Good for you!" can also be translated as informal "Красавчик" in order to show your personal reaction (to say someone's really good at what he does).
As for "тебе на пользу" in "eating healthy food is good for you", it's better to say "есть здоровую еду полезно", without "тебе", or translate it "здоровая еда для тебя полезна", it's much closer to what natives say to each other.