What problem does it solve? Database-touching test suites often suffer from order-dependent failures, leaked connections, and slow manual cleanup code. This Skill encodes the counter-intuitive rules of a template-database + per-worker-clone + global-truncate architecture so tests stay isolated without any hand-written teardown. ## Core Features & Use Cases - Cleanup elimination: Explains why deleteMany, DELETE FROM, ID tracking, and manual rollback in afterEach/afterAll are bugs under this harness, since a global truncate already wipes every table. - Concurrency and transaction guardrails: Prevents raw BEGIN statements on pooled clients, forbids test.concurrent in DB-touching files, and bans row creation in beforeAll that later tests depend on. - Failure diagnosis: Maps symptoms like "passes alone but fails in the suite", "row not found after the first test", and connection-pool exhaustion to their architectural root causes. - Use Case: When writing a Vitest suite for a repository layer against a Postgres test database, load this Skill before adding beforeEach hooks or teardown logic to avoid cleanup code that fights the harness. ## Quick Start Review my database test file and tell me whether the cleanup and setup hooks follow the test-isolation rules.
