edge-case-hunterlisted

# Edge Case Hunter ## Goal Produce an edge-case inventory for a capability before implementation starts. The goal is not to block delivery; it is to force hard cases into design time instead of QA or production. ## When To Use - **F3 Design** — before closing design and moving to implementation. - **F4 Validation** — pre-merge review when design skipped edge-case review. ## Checklist Answer every dimension. A "not applicable" answer must include a one-line justification. ### 1. Invalid Or Boundary Input - [ ] Empty, null or undefined input. - [ ] Zero-size input: empty array, empty string, object without properties. - [ ] Valid min and max boundary. - [ ] Just outside valid boundary. - [ ] Wrong types. ### 2. Concurrency And Shared State - [ ] Two users execute the same operation on the same resource. - [ ] Read/write race condition. - [ ] Retry after partial state change. ### 3. Partial Failure And Recovery - [ ] Step N fails after step N-1 already changed state. - [ ] Rollback or explicit partial-state handling. - [ ] Error message names the failing step enough for recovery. ### 4. External Dependencies - [ ] External service timeout. - [ ] Unexpected response shape. - [ ] Retry idempotency. ### 5. Authorization And Privacy - [ ] User changes an ID in the URL or payload. - [ ] Logs or errors expose sensitive data. - [ ] Permission validation happens on the server, not only in UI. ### 6. Volume And Performance - [ ] Large result set. - [ ] Required indexes