Testing

How to write effective tests and run them successfully.

When to Use

• Writing unit, integration, or E2E tests
• Debugging test failures
• Reviewing test quality
• Deciding what to mock vs use real implementations

Layer Distribution

• Unit (60-70%): Mock at boundaries only
• Integration (20-30%): Real deps, mock external services only
• E2E (5-10%): No mocking - real user journeys