Assignment Completed: Added Unit & Integration testing, fix pagination/priority bugs, implement task assignment endpoint

[Adamkoda2306]

Summary

This pull request improves the reliability and maintainability of the Task Manager API by adding comprehensive automated tests, fixing identified bugs, and implementing a new task assignment feature.

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Changes Made

✅ Added Unit Tests

Implemented 28 unit tests for the taskService covering:

• Task creation
• Retrieving all tasks
• Finding tasks by ID
• Filtering tasks by status
• Updating tasks
• Deleting tasks
• Completing tasks
• Pagination
• Statistics
• Task assignment

✅ Added Integration Tests

Implemented 32 API integration tests using Supertest for all endpoints, including the new one:

• GET /tasks
• GET /tasks?status=
• GET /tasks?page=&limit=
• POST /tasks
• PUT /tasks/:id
• DELETE /tasks/:id
• PATCH /tasks/:id/complete
• PATCH /tasks/:id/assign
• GET /tasks/stats

The tests cover both successful requests and common error scenarios such as invalid input and missing resources.

✅ Bug Fixes

Pagination Bug

• Fixed incorrect pagination offset calculation.
• Updated the offset formula from page * limit to (page - 1) * limit so the first page returns the correct records.

Task Completion Bug

• Fixed an issue where completing a task unintentionally reset its priority to "medium".
• Task completion now updates only the task status and completion timestamp while preserving the existing priority.

✅ New Feature

Implemented a new endpoint:

PATCH /tasks/:id/assign

Features include:

• Assigns an assignee to an existing task.
• Returns the updated task.
• Returns 404 Not Found if the task does not exist.
• Returns 400 Bad Request for invalid or empty assignee values.
• Added both unit and integration tests for the new endpoint.

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Test Coverage

Coverage results:

Metric	Coverage
Statements	94.8%
Branches	90.8%
Functions	93.33%
Lines	94.28%

A total of 60 automated tests have been added (28 unit, 32 integration), all of which are passing.

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Testing

Executed:

npm test
npm run coverage

Result:

• ✅ 60/60 tests passing
• ✅ All endpoints verified
• ✅ New feature fully tested
• ✅ Existing bugs identified and resolved

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