Just This Once
The test is tomorrow and the whole class already has the answers. Someone found last year's paper online and it turns out the teacher reused every question. By lunchtime, a copy has reached almost everyone. "Just this once," they say. "Everyone's doing it. It's not like anyone gets hurt."
You could read it. One look and a hard test becomes an easy one. Nobody would ever know. And the argument sounds reasonable: the teacher made the mistake, not you. You didn't go looking for it. If everyone else scores high and you don't, you're the one who loses out.
But pull on the thread a little. If everyone scores high, the teacher might think the class understood the material — and move on to something harder that nobody is ready for. The marks stop meaning anything. And "no one gets hurt" is doing a lot of quiet work in that sentence. Maybe the person hurt is a future version of you, sitting in next year's class without the thing this test was supposed to teach you.
There's also the question of what "everyone's doing it" actually proves. A lot of people doing something doesn't make it right — it just makes it common. And "just this once" has a way of becoming "just one more time."
You could refuse and sit the test honestly, and maybe score lower than people who cheated. You could refuse and tell the teacher, and become the person who got the class in trouble. You could read it and tell yourself it doesn't really count.
Every option costs something — a mark, a friendship, or a small piece of how you see yourself. So which cost are you willing to pay, and which one can you actually live with? Talk it through. Notice what changes when you imagine someone doing the exact same thing to you.