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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:

  1. Red: Write a failing test
  2. Green: Write minimal code to pass
  3. 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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