Agent Skills: Testing Rules

Testing Rules

These rules are mandatory for all test-related work.

TDD Workflow

RED → GREEN → REFACTOR (all new code).

Test Strategy

| Layer | Test Type | Mock Strategy | |-------|-----------|---------------| | Functional Core | Unit Test | No mocks needed (pure input→output) | | Imperative Shell | Integration | Testcontainers (real DB/services) | | External APIs | Test Double | With // Test Double rationale: [reason] |

Forbidden Patterns

These patterns are never acceptable:

| Pattern | Why Forbidden | Alternative | |---------|---------------|-------------| | jest.fn() for Repository/Service/Domain | Invalid test — doesn't prove production works | Testcontainers | | class InMemoryRepository | Diverges from real DB behavior | Real DB container | | class MockXxx / class FakeXxx | Hides integration issues | Direct instantiation or Testcontainers | | jest.mock('../services/X') | Skips real collaboration | Test real collaboration | | it.skip('...database...') | "Too slow" is not valid | Testcontainers are fast enough |

Coverage Requirements

• 80% overall minimum
• 100% Functional Core (pure logic must be fully tested)
• Critical paths for Imperative Shell

Dev/Prod Parity

Tests must use real dependencies:

• Real database via Testcontainers (not in-memory substitutes)
• Config via environment variables
• Mock tests passing ≠ production working

Detection Checklist

When analyzing test files, flag:

1. Any jest.fn() usage on Repository, Service, or Domain classes
2. Any InMemory* or Mock* or Fake* class definitions
3. Any jest.mock() calls on internal modules
4. Any skipped tests with database/slow excuses
5. Missing error case coverage
6. Missing edge case coverage