springboot-testing

name	springboot-testing
description	Use this skill when writing, structuring, or refactoring tests in Spring Boot applications to ensure reliability, correctness, and architectural alignment.

When testing Spring Boot applications:

1. Follow testing levels:

   • unit tests → domain and use-cases (no Spring context)
   • integration tests → adapters, repositories, controllers
   • e2e tests → full application flow

2. Test use-cases (application layer):

   • isolate from framework and infrastructure
   • mock all external dependencies (ports)
   • validate business rules and orchestration
   • test multiple scenarios, not just success

3. Test domain logic:

   • use pure unit tests
   • validate business invariants
   • cover edge cases and invalid states

4. Test controllers:

   • use @WebMvcTest or similar
   • mock use-cases
   • validate request/response mapping
   • verify HTTP status codes and payloads

5. Test repositories:

   • use @DataJpaTest or integration tests
   • validate queries and persistence behavior
   • use in-memory or testcontainers databases

6. Structure tests as:

   • Arrange → setup inputs and mocks
   • Act → execute behavior
   • Assert → verify outputs and side effects

7. Never test only the happy path:

   • include failure scenarios
   • test invalid inputs
   • test edge cases and boundary conditions
   • validate exception handling and error propagation

8. Mock dependencies properly:

   • mock ports in use-cases
   • avoid mocking domain logic
   • use mocks to isolate behavior, not to hide complexity

9. Ensure isolation:

   • tests must not depend on external systems
   • avoid shared mutable state between tests
   • keep tests deterministic and repeatable

10. Validate error handling:

    • assert thrown exceptions
    • verify correct error mapping in controllers
    • test both business and technical failures

11. Avoid:

    • loading full Spring context for unit tests
    • testing implementation details instead of behavior
    • flaky tests dependent on timing or environment
    • duplicating test logic

12. Refactor by:

    • splitting large tests into focused cases
    • removing unnecessary framework dependencies
    • introducing mocks for external dependencies
    • improving test readability and intent

13. Ensure:

    • high coverage of business logic
    • confidence in refactoring
    • alignment with Clean Architecture boundaries
    • fast and reliable test execution

If tests only validate the happy path, depend on real infrastructure, or are tightly coupled to implementation details, they violate this skill.