Teacher copy: This page may include teaching prompts or answer keys. Answer keys in this public library can be viewed by anyone. Give learners a clean prompt, use checks as formative evidence, and change a case locally when prior access matters.
Encounter/model: Pretend prism tokens use input<4 ADD1 otherwise ADD3. Input4 chooses3; changing to≤4 chooses1. This comparison boundary matters even if most inputs agree.
Own practical action: Choose a meaningful comparison/update change; predict a separating record. Run both sides and the exact boundary, then repair whichever version misses the criterion. Inspect SET placement too if state differs.
Observe/check: Is the test selected to reveal a difference, rather than just rerunning a familiar output?
Possible misconception: Using only one convenient record and declaring every branch correct.
Next teaching move: Offer the closest exact boundary and an alternative outcome, with no speed requirement.
Use: choose one route, one model or neither where unnecessary. No30-route log or all-context quota. Home/extra 7 is an independent free offer, not required catch-up.