We can directly ask if they are confident for the test. But to make it more simple and natural, you can ask if they are ready for the test. If you are ready then you would be prepared and maybe confident but most people never feel fully confident about a test.
テストで自信があるか直接的に聞くことができますが、もっとシンプルで自然な表現にするには、ready for the testというフレーズを使うといいでしょう。もし、何かに対して準備ができているのなら、それが自信につながることですが、ほとんどの人はテストで完全に自信があるというふうに感じることはないかもしれまんね。
*Are you ready/prepared about.....?
Depending on what it is you asking about you can say ready or prepared.
If it is about the test you can say " Are you prepared/ready for your test tomorrow"or " Are you ready/prepared for your tennis match tomorrow". This means you want to know if they are confident .
*Are you ready/prepared about.....?
～の準備はできている？（自信はある？）
何について聞くかにもよりますが、readyかprepareを使うことができます。もしテストであれば、
" Are you prepared/ready for your test tomorrow"
明日のテストの準備はできている？
と、聞くことができます。
" Are you ready/prepared for your tennis match tomorrow？"
明日のテニスの試合は自信ある？
これは、相手が自信があるか聞きたいという意味です。
How confident do you feel about the test tomorrow?
Do you feel confident about the bike race next week?
Confidence is a feeling so I would ask them how they feel about the specific event. You can ask "how confident do you feel" which allows the person who you are talking to, to give a more open answer. The second sentence, with "do you feel confident" generally will end with a yes or no response if you are looking for something more specific.
Confidence（自信）は感情なので、私ならある特定の出来事についてどう感じているか聞くでしょう。
"how confident do you feel"
どのくらい自信がありますか？
これは、話している相手に、自由に答えてもらう質問です。
二つ目の文の、"do you feel confident" （自信はありますか？）は、一般的に、はいかいいえで答える質問です。
1. Are you brimming with confidence about the coming race?
2.What level of confidence do you have for tomorrow's race?
1. You may put a closed question to your friend to enquire about their level of certainty that they will perform well in the race.
If you are 'brimming with confidence' it means that you are very confident you will do well.
2. An open question and your friend should respond explaining exactly how confident they are and perhaps adding a little more information of interest.
1つ目の例は、試合やレースでうまくやる自信があるかを聞く、はい、いいえで答えられる質問です。
'brimming with confidence'とは、とても自信があって、うまくいきそうだという意味です。
2つ目の例は、自由に回答できる質問で、友達がどれほど自信があって、それについてもう少し説明してくれると思います。
Are you feeling confident about the match/test/race tomorrow?
Do you feel prepared for the test/match/race tomorrow?
When you want to find out from a friend whether they are feeling confident about a sports game/match, test or race tomorrow; then you may ask in the following ways:
-Are you feeling confident about the match/test/race tomorrow?
-Do you feel prepared for the test/match/race tomorrow?
-Do you have a good feeling about the race tomorrow?
スポーツの試合やレース、テストなどについて、友達に「自信はありますか」と聞きたいということですね。次のように言えます。
-Are you feeling confident about the match/test/race tomorrow?（明日の試合／テスト／レースは自信がありますか）
-Do you feel prepared for the test/match/race tomorrow?（明日のテスト／試合／レースは自信がありますか）
-Do you have a good feeling about the race tomorrow?（明日のレースは自信がありますか）
Are you feeling positive about your test tomorrow?
Are you feeling assured about your ability to perform well in the test tomorrow?
Are you confident about the test tomorrow?
If you want to ask someone about how they feel about the test tomorrow, and whether they are confident or not, you can ask the following questions:-
1. Are you feeling positive about your test tomorrow?
If you are feeling confident about a test it means that you have a sense of surety that you will do well on the test.
2. Are you feeling assured about your ability to perform well in the test tomorrow?
To feel "assured" about something, it means that you are confident about that thing.
3. Are you confident about the test tomorrow?
「あしたのテストは自信がありますか」は、次のように言えます。
1. Are you feeling positive about your test tomorrow?（あしたのテストは自信がありますか）
"Are you feeling positive about your test" で「テストでよい点を取る自信はありますか」という意味になります。
2. Are you feeling assured about your ability to perform well in the test tomorrow?（あしたのテストは自信がありますか）
"assured" は「自信のある／確信を持った」という意味です。
3. Are you confident about the test tomorrow?（あしたのテストは自信がありますか）
Are you feeling optimistic about winning the game?
You can use the word "prepared" to show that you're ready for or certain about an upcoming event.
Ex. I am prepared to provide evidence that my client did not commit this crime.
"to get ready" or "to be ready" can be used to show that one is "set", "prepared" or "primed" to perform an action.
Ex. I'm ready to go to school now.
One can feel "optimistic" about the outcome of an upcoming event. This means one can have positive feelings or thoughts about the future, which can also mean one feels confident that the future will be bright.
Ex. I'm optimistic about my chances of getting a book deal.
"prepared" は「準備はできている」「自信はある」と表したいときに使えます。
例：
I am prepared to provide evidence that my client did not commit this crime.（依頼人が無実だという証拠を示すことができる）
"to get ready" または "to be ready" は「準備は整っている」という意味を表します。
例：
I'm ready to go to school now.（学校に行く準備はできました）
"optimistic" は「楽観的な」という意味です。これも「自信がある」という意味を表します。
例：
I'm optimistic about my chances of getting a book deal.（出版契約を取れるのではないかと思っている）
The first two example sentences can be used interchangeably as the only thing that changes are the words, "prepared," and, "ready." These two words within the test ask if someone is feeling confident about the test.
The last example is using the word, "confident," directly when asking the question. Notice how we would use the verb, "to feel," as confidence is an emotion that we can feel.
Are you well prepared for what's to come tomorrow?
How are you feeling for tomorrow?
You could use 'prepared/confident' when asking the question and they will be able to give you a direct answer to your question.
When saying 'How are you feeling for tomorrow?' this could have a more open approach when the person responds as they could then explain how they are feeling.
ここでは、'prepared' や 'confident' を使えば、ストレートに回答が返ってきます。
'How are you feeling for tomorrow?'（あしたに向けて今どんな気持ちですか）
これはよりオープンな質問です。相手は自分の気持ちについて自由に答えることができます。
How do you feel about the competition/test tomorrow?
Do you feel confident about the test/competition tomorrow?
If you would like to ask someone how they are feeling or if they feel confident about an upcoming test/competition, you can do so by saying something like "How do you feel about the competition/test tomorrow?" or "Do you feel confident about the test/competition tomorrow?".
間もなく行われるテストや試合について「自信はありますか」と聞きたいなら、次のように言えます。
"How do you feel about the competition/test tomorrow?"（明日の試合／テストは自信がありますか）
"Do you feel confident about the test/competition tomorrow?"（明日の試合／テストは自信がありますか）
「自身がありますか？」は
Are you confident?と言います(*^_^*)
あとは、confidentという単語を知らなければ、
Do you think you can pass the test?
「試験に合格できると思いますか？」
のように具体的に言っても良いですね♪
以上です。
少しでも参考になれば幸いです(*^_^*)
イギリス 
南アフリカ 
アメリカ合衆国 
カナダ 
日本 
