Test-Driven Development
Implement Test-Driven Development (TDD) workflows with Claude Code to build robust, well-tested applications with confidence.
TDD Fundamentals
The Red-Green-Refactor Cycle
Claude Code enhances the traditional TDD cycle:
- Red: Write a failing test
- Green: Write minimal code to pass
- Refactor: Improve code while keeping tests green
Getting Started with TDD
I want to implement a user authentication system using TDD.
Let's start by writing tests for the login functionality.
Claude will:
- Help design comprehensive test cases
- Suggest edge cases to consider
- Create test structure following best practices
- Guide implementation step by step
TDD Workflow with Claude
1. Test Planning
Define Requirements:
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?
Test Case Design:
Create comprehensive test cases for a user registration system that includes:
- Email validation
- Password strength requirements
- Duplicate email handling
- Database integration
2. Writing Tests First
Unit Tests:
Write unit tests for a calculateTotal function that:
- Adds item prices
- Applies discounts
- Handles tax calculation
- Manages currency formatting
Integration Tests:
Create integration tests for the user authentication API that test:
- Login endpoint
- Token generation
- Session management
- Error handling
3. Implementation Guidance
Minimal Implementation:
I have these failing tests for a user service.
Help me write the minimal code to make them pass:
[paste test code]
Iterative Development:
My tests are passing but the code needs refactoring.
Help me improve it while keeping all tests green.
Advanced TDD Patterns
Behavior-Driven Development (BDD)
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
Test Doubles and Mocking
Create mocks for external dependencies in my payment processing tests:
1. Payment gateway API
2. Database connections
3. Email service
4. Logging system
Property-Based Testing
Implement property-based tests for my string utility functions:
1. Test with random inputs
2. Verify invariants hold
3. Find edge cases automatically
Testing Strategies
Frontend TDD
Component Testing:
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
E2E Testing:
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
Backend TDD
API Testing:
Write comprehensive API tests for a REST endpoint:
1. Valid request/response cycles
2. Authentication and authorization
3. Input validation
4. Error handling
Database Testing:
Create database tests that:
1. Test CRUD operations
2. Verify data integrity
3. Check constraint enforcement
4. Test transaction handling
Test Organization
Test Structure
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
Test Data Management
Set up test data management:
1. Create test fixtures
2. Implement data factories
3. Manage test database state
4. Handle test isolation
Continuous Testing
Set up continuous testing pipeline:
1. Run tests on every commit
2. Parallel test execution
3. Test result reporting
4. Failure notifications
Common TDD Challenges
Legacy Code Testing
I have legacy code without tests. Help me:
1. Add characterization tests
2. Refactor safely
3. Improve testability
4. Gradually increase coverage
Testing Complex Logic
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
Performance Testing
Create performance tests that:
1. Measure response times
2. Test under load
3. Identify bottlenecks
4. Verify scalability
Best Practices
Test Quality
- Clear Test Names: Describe what is being tested
- Single Responsibility: One assertion per test
- Independent Tests: No dependencies between tests
- Fast Execution: Keep tests quick to run
Code Coverage
Analyze test coverage and identify:
1. Untested code paths
2. Missing edge cases
3. Integration gaps
4. Critical areas needing more tests
Test Maintenance
Refactor tests to:
1. Reduce duplication
2. Improve readability
3. Update for code changes
4. Remove obsolete tests
Tools and Frameworks
JavaScript/TypeScript
- Jest: Unit and integration testing
- Cypress: E2E testing
- Testing Library: Component testing
- Supertest: API testing
Python
- pytest: Comprehensive testing framework
- unittest: Built-in testing
- Selenium: Browser automation
- requests-mock: HTTP mocking
Java
- JUnit: Unit testing
- Mockito: Mocking framework
- TestContainers: Integration testing
- Selenium: E2E testing
Measuring Success
Metrics to Track
Track TDD effectiveness:
1. Test coverage percentage
2. Bug detection rate
3. Development velocity
4. Code quality metrics
Continuous Improvement
Regularly review and improve:
1. Test suite performance
2. Test reliability
3. Development workflow
4. Team practices
By following TDD practices with Claude Code, you’ll build more reliable software, catch bugs early, and maintain confidence in your codebase as it evolves.
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