Test-Driven Development

I want to implement a user authentication system using TDD. 
Let's start by writing tests for the login functionality.

I need to implement a shopping cart feature. Help me plan the tests:
1. What functionality should be tested?
2. What edge cases should I consider?
3. How should I structure the test suite?

Create comprehensive test cases for a user registration system that includes:
- Email validation
- Password strength requirements
- Duplicate email handling
- Database integration

Write unit tests for a calculateTotal function that:
- Adds item prices
- Applies discounts
- Handles tax calculation
- Manages currency formatting

Create integration tests for the user authentication API that test:
- Login endpoint
- Token generation
- Session management
- Error handling

I have these failing tests for a user service. 
Help me write the minimal code to make them pass:
[paste test code]

My tests are passing but the code needs refactoring. 
Help me improve it while keeping all tests green.

Convert these user stories into BDD-style tests:
- As a user, I want to add items to my cart
- As a user, I want to remove items from my cart
- As a user, I want to see my cart total

Create mocks for external dependencies in my payment processing tests:
1. Payment gateway API
2. Database connections
3. Email service
4. Logging system

Implement property-based tests for my string utility functions:
1. Test with random inputs
2. Verify invariants hold
3. Find edge cases automatically

Write tests for a React component that:
1. Renders correctly with props
2. Handles user interactions
3. Manages internal state
4. Integrates with external APIs

Create end-to-end tests for the user registration flow:
1. Navigate to registration page
2. Fill out form with valid data
3. Submit and verify success
4. Test error scenarios

Write comprehensive API tests for a REST endpoint:
1. Valid request/response cycles
2. Authentication and authorization
3. Input validation
4. Error handling

Create database tests that:
1. Test CRUD operations
2. Verify data integrity
3. Check constraint enforcement
4. Test transaction handling

Organize my test suite for a large application:
1. Unit tests by module
2. Integration tests by feature
3. E2E tests by user journey
4. Performance tests by scenario

Set up test data management:
1. Create test fixtures
2. Implement data factories
3. Manage test database state
4. Handle test isolation

Set up continuous testing pipeline:
1. Run tests on every commit
2. Parallel test execution
3. Test result reporting
4. Failure notifications

I have legacy code without tests. Help me:
1. Add characterization tests
2. Refactor safely
3. Improve testability
4. Gradually increase coverage

Write tests for complex business logic:
1. Break down into smaller units
2. Test each component separately
3. Verify integration points
4. Handle edge cases

Create performance tests that:
1. Measure response times
2. Test under load
3. Identify bottlenecks
4. Verify scalability

Analyze test coverage and identify:
1. Untested code paths
2. Missing edge cases
3. Integration gaps
4. Critical areas needing more tests

Refactor tests to:
1. Reduce duplication
2. Improve readability
3. Update for code changes
4. Remove obsolete tests

Track TDD effectiveness:
1. Test coverage percentage
2. Bug detection rate
3. Development velocity
4. Code quality metrics

Regularly review and improve:
1. Test suite performance
2. Test reliability
3. Development workflow
4. Team practices