test: unit tests useTodos Hook

[perzeuss]

🧪 Add Unit Tests for useTodos Hook

📋 Overview

Create comprehensive unit tests for the useTodos custom hook to ensure all CRUD operations, error handling, and state management work correctly.

🎯 Acceptance Criteria

• Test file hooks/use-todos.spec.ts is created
• Tests cover all hook functions: addTodo, updateTodo, toggleTodo, deleteTodo
• Tests verify loading states and error handling
• API calls are properly mocked
• Tests ensure state updates correctly after operations
• All tests pass with npm test

🔧 Technical Requirements

• Use Jest + React Testing Library
• Mock fetch API calls
• Test both success and error scenarios
• TypeScript support for test files

🚫 Out of Scope

• Integration tests with real API
• Component integration testing
• End-to-end testing scenarios
• Performance testing
• Testing Next.js specific features

📚 Resources

• Jest Mocking Guide
• React Testing Library
• Next Testing Guide

💡 Testing Tips

• Test one function at a time
• Always test both happy and unhappy cases
• Use descriptive test names
• Mock external dependencies