Backend with Java · the first exercise in each domain is free

Review the AI's code

AI writes a lot of code now. Knowing whether it's right is the job. In each exercise Aria hands you code from a real kind of business (a clinic's booking API, a UPI-style wallet, an online store, a food-delivery app) that looks correct and has one real flaw. You prove the bug with a JUnit test that fails on her code, then fix it so your test and our hidden checks pass.

1. 1. Read Aria's code, as she wrote it
2. 2. Prove a test that fails on her code and passes on correct code
3. 3. Fix the code, then pass your test and our checks