Skill: backend/backend-test-additions

Purpose

Add backend tests that prove:

• domain invariants
• endpoint behavior and error mapping
• job behavior (idempotency/retries) where applicable
• integration adapter parsing and failure handling

Prefer deterministic, high-signal tests.

Inputs

• Target module/endpoint/job
• Behavior to validate (acceptance criteria)
• Existing test stack and conventions (from repo/profile)
• Mocking strategy (fixtures, fakes, contract tests) if present