Tutorial Library

Add unit tests for the UserService class in src/services/user.js.

Current coverage: 35%
Target coverage: 80%

Requirements:
1. Test all public methods
2. Cover edge cases (null inputs, empty arrays, etc.)
3. Mock external dependencies (database, API calls)
4. Follow our existing test patterns in tests/services/
5. Use Jest as the testing framework

Focus on these methods:
- createUser()
- updateUser()
- deleteUser()
- getUserById()

Add integration tests for the /api/products endpoints.

Endpoints to test:
- GET /api/products (list all)
- GET /api/products/:id (get one)
- POST /api/products (create)
- PUT /api/products/:id (update)
- DELETE /api/products/:id (delete)

Requirements:
1. Use our test database (configured in jest.config.js)
2. Set up and tear down test data properly
3. Test success cases and error cases
4. Verify response bodies and status codes
5. Follow patterns in tests/integration/

Create a Python script to analyze our sales data.

Input: sales_data.csv with columns: date, product, quantity, price, region

Requirements:
1. Load and validate the CSV data
2. Calculate:
   - Total revenue by product
   - Monthly sales trends
   - Top 5 products by quantity
   - Revenue by region
3. Generate a summary report (Markdown format)
4. Create visualizations (bar chart for top products, line chart for trends)
5. Save results to reports/ directory

Use pandas for data processing and matplotlib for charts.

Analyze our slow query log and identify optimization opportunities.

File: logs/slow_queries.log

For each slow query:
1. Explain why it's slow
2. Suggest index additions if helpful
3. Rewrite the query if it can be optimized
4. Estimate the improvement

Create a report in reports/query_optimization.md with:
- Summary of findings
- Prioritized recommendations
- SQL for suggested changes

Create a web scraper to extract product information from our competitor's site.

Target URL: https://example-store.com/products

Extract for each product:
- Name
- Price
- Description
- Image URL
- SKU (if available)

Requirements:
1. Use Python with BeautifulSoup or Scrapy
2. Handle pagination (site has 50 pages)
3. Respect rate limits (1 request/second)
4. Save results to products.json
5. Handle errors gracefully
6. Log progress to console

Include a README with usage instructions.

Review this pull request for security issues:

Focus areas:
1. Input validation - check all user inputs are sanitized
2. Authentication - verify auth checks are in place
3. SQL injection - check for parameterized queries
4. XSS - verify output encoding
5. Sensitive data - ensure no secrets in code

For each issue found, provide:
- File and line number
- Severity (Critical/High/Medium/Low)
- Description of the vulnerability
- Suggested fix with code example

Output format: Markdown suitable for PR comments

Review the OrderService class for performance issues.

File: src/services/order.js

Check for:
1. N+1 database queries
2. Missing indexes (based on query patterns)
3. Inefficient loops or algorithms
4. Missing caching opportunities
5. Unnecessary data fetching

For each issue:
- Explain the impact
- Show the problematic code
- Provide an optimized version
- Estimate the improvement

Fix the crash in the checkout process.

Error:
TypeError: Cannot read property 'price' of undefined
  at calculateTotal (src/checkout/calculator.js:45)
  at processOrder (src/checkout/processor.js:23)

Steps to reproduce:
1. Add item to cart
2. Apply discount code "SAVE20"
3. Click checkout
4. Crash occurs

The bug was introduced in commit abc123 (yesterday's deployment).

Requirements:
1. Identify the root cause
2. Fix the bug
3. Add a regression test
4. Verify the fix doesn't break other functionality

Investigate and fix the memory leak in our Node.js application.

Symptoms:
- Memory usage grows 100MB/hour
- After 24 hours, app becomes unresponsive
- Restarting temporarily fixes the issue

Suspected areas:
- Event listeners in src/events/
- Cache implementation in src/cache/
- WebSocket connections in src/ws/

Analyze these areas and:
1. Identify the leak source
2. Explain why it's leaking
3. Implement a fix
4. Add monitoring to detect future leaks

Add a user preferences API endpoint.

Endpoint: /api/users/:id/preferences

Operations:
- GET: Retrieve user preferences
- PUT: Update user preferences
- PATCH: Partially update preferences

Preferences schema:
{
  theme: "light" | "dark",
  notifications: { email: boolean, push: boolean },
  language: string,
  timezone: string
}

Requirements:
1. Follow patterns in src/api/routes/
2. Add request validation with Joi
3. Use UserPreferencesService for business logic
4. Add appropriate error handling
5. Document the endpoint in OpenAPI format
6. Add unit and integration tests

Implement a feature flag system for our application.

Requirements:
1. Create a FeatureFlags service
2. Support these flag types:
   - Boolean (on/off)
   - Percentage (gradual rollout)
   - User-based (specific user IDs)
3. Load flags from environment variables initially
4. Add a React hook: useFeatureFlag(flagName)
5. Add middleware for API routes

Initial flags to configure:
- new_checkout: boolean, default false
- dark_mode: percentage, default 10%
- beta_features: user-based

Include documentation and tests.