Take-home: add full test coverage, fix core API bugs, and implement task assignment endpoint

[nikkkhil2935]

Submission Notes

Summary

• Added a full test suite covering service, validators, routes, and app bootstrap behavior
• Implemented PATCH /tasks/:id/assign with payload validation, conflict handling, and idempotent repeat behavior
• Added GET /tasks/:id for direct single-task retrieval
• Added optional ?assignee= filtering on GET /tasks
• Fixed multiple behavior defects discovered through test-driven development
• Documented all findings in task-api/BUG_REPORT.md with root-cause analysis and fix rationale

---

Bugs Fixed

#	Location	Defect
1	taskService.js → getPaginated	Pagination off-by-one — page * limit skipped the first page entirely
2	taskService.js → getByStatus	Status filter used partial string match instead of exact enum equality
3	taskService.js → completeTask	Completion flow silently reset priority to medium
4	taskService.js → update	Unrestricted object spread allowed id and createdAt to be overwritten
5	routes/tasks.js + validators.js	No validation on status, page, or limit query params

---

Design Decisions

PATCH /tasks/:id/assign returns 409 Conflict on reassignment
The request payload is valid, but it conflicts with current ownership state. 409 is semantically correct here — it signals a state conflict, not a client input error, which distinguishes it from 400 Bad Request.

Idempotent repeat assignment returns 200 OK
Repeating the same assignee is treated as a no-op success. This keeps the operation retry-safe and consistent with REST idempotency principles — the resource state does not change, so 201 would be misleading.

Assignee filtering is case-insensitive
Clients may send Alice, alice, or ALICE depending on their input layer. Case-insensitive matching at the service boundary prevents silent filter misses without requiring callers to normalize strings.

Update uses a mutable-field allow-list
Rather than blocking specific immutable fields, the update flow only accepts an explicit set of mutable fields: title, description, status, priority, dueDate, assignee. Unknown or immutable keys (including id and createdAt) are silently ignored, protecting data integrity without throwing errors on extra fields.

---

Test Results

Test Suites: 4 passed, 4 total
Tests: 47 passed, 47 total
Coverage: 100% statements | 100% branches | 100% functions | 100% lines