Workflow
Test Generation
Add coverage for edge cases and critical paths quickly.
Overview
Writing comprehensive tests is time-consuming, but skipping them leads to production bugs and regression issues. Claude Code accelerates test creation by analyzing your code, identifying edge cases, and generating test suites with proper assertions and mocking. Instead of spending hours writing boilerplate test code, you can focus on reviewing test logic and ensuring critical paths are covered.
Use this workflow when adding tests to existing code, increasing coverage for critical paths, validating edge cases and failure modes, implementing TDD for new features, or preparing code for refactoring.
Step-by-step process
Describe the function or module under test
Provide context about what the code does, its inputs and outputs, and any dependencies or side effects. Include information about the testing framework you're using.
Ask for edge cases and failure modes
Request that Claude identify boundary conditions, error scenarios, and unexpected inputs that your tests should handle.
Generate tests with clear assertions
Have Claude create test cases with descriptive names, proper setup/teardown, meaningful assertions, and appropriate mocking.
Run the suite and review failures
Execute the generated tests, analyze any failures, and iterate on test implementation or the underlying code as needed.
Example prompts
"This auth.service.ts file has no tests. Analyze it and create a comprehensive test suite covering user registration, login, token refresh, and error handling. Mock the database calls."
"Generate tests for the UserProfile component using React Testing Library. Test rendering with different prop combinations, user interactions (button clicks, form submissions), loading states, and error states."
"Create integration tests for the POST /api/orders endpoint. Test successful order creation, validation errors, authentication failures, and rate limiting. Use supertest and mock the payment gateway."
"Our payment processing module has 40% test coverage. Identify the most critical untested code paths and generate tests for them, prioritizing transaction handling and refund logic."
Expected outputs
Test plan
Structured outline of test categories, edge cases to cover, and testing strategy tailored to your codebase
New tests
Complete test files with proper imports, setup/teardown, mocking, descriptive test names, and meaningful assertions
Coverage notes
Analysis of what's tested, what's missing, and recommendations for achieving comprehensive coverage
Mock implementations
Reusable mock objects, stubs, and fixtures for external dependencies like databases, APIs, and third-party services
Best practices
Common pitfalls
Generating tests without understanding test quality
Solution: Ask Claude to explain why each test is important and what specific behavior it validates. Don't just blindly accept generated tests.
Over-mocking and testing implementation instead of behavior
Solution: Request integration tests alongside unit tests. Ask Claude: 'Are we testing behavior or implementation here?'
Not running tests after generation
Solution: Always run the test suite immediately after generation. Fix any failures before moving on to ensure tests are actually valid.
Pro tips
Generate tests alongside new features
""I'm building a new comment system. Write the tests first based on these requirements, then we'll implement the code to pass them.""
Use coverage reports to guide test generation
""Here's our coverage report showing 60% coverage. Analyze the uncovered lines and generate tests to get us to 85%.""
Create reusable test utilities
""Extract the common setup code from these tests into a test factory. I want to reuse user creation and authentication mocks across test files.""