Mock/Fixture Design

Design test doubles, factories, and fixtures for reliable test infrastructure.

Test Creation Checklist

Mock Object Design

• Define clear interfaces for all mockable dependencies
• Configure mock return values matching realistic production data
• Set up verification for expected interaction counts and order
• Avoid over-mocking by using real implementations where practical
• Ensure mocks fail fast with descriptive error messages

Stub & Fake Implementation

• Create lightweight fake implementations for complex dependencies
• Implement configurable stubs that support multiple test scenarios
• Verify fakes maintain behavioral parity with real implementations
• Provide error simulation modes (network failure, timeout, corruption)
• Keep fake implementations simple and avoid duplicating production logic

Test Data Factories

• Build factories that produce valid default objects with minimal setup
• Support trait-based customization for specific test scenarios
• Ensure generated data satisfies all validation constraints
• Provide sequence generators for unique identifiers and timestamps
• Create related object graphs with proper foreign key relationships

Fixture Management

• Organize shared fixtures by domain context, not by test file
• Implement setup/teardown that guarantees clean state between tests
• Use fixture scoping (test, class, module) appropriate to cost
• Version control seed data alongside schema migrations
• Document fixture dependencies and loading order requirements

Output Format

Report test plan with priority ratings: