test-guide - SKILL.md Agent Skill

name: test-guide description: > Guide for writing tests following the project's layered test standards. Use when the user says "write tests", "add tests", "test strategy", "what tests to write", "test this module", "where should this test go", or is deciding which test layer to use.

Test Standards

Each test justifies its infrastructure cost. No duplicate assertions across layers.

Decision Flowchart

Input validation rules?           → Value object unit test
SQL behavior (constraints, JOINs)? → Repository test
Auth, ownership, business rules?   → Service test
HTTP status, response shape?       → Router test
Happy-path CRUD flow?              → Router test (covers all layers)

Layer Guide

Value Objects — Pure Unit Tests

Infra: None (#[test], sync, no I/O) Test: validation rules, normalization, rejection messages, boundary values

Repository — SQL Correctness

Infra: Shared TestDb Test: constraints (unique, CHECK, FK), JOINs, ltree paths, complex queries, pagination SQL Skip: CRUD happy paths (covered by router tests)

Service — Business Logic & Auth

Infra: Shared TestDb Test: auth guards (require_admin, require_access), ownership checks, FK validation, cache behavior, complex workflows (password hashing, token generation) Skip: CRUD happy paths, HTTP status codes, request deserialization

Router — HTTP Contract

Infra: Shared TestDb + full axum router via tower::oneshot Test: happy-path CRUD, HTTP status codes, auth middleware (401/403), request deserialization (422), response shape, pagination, filters, multi-step flows Skip: SQL constraint details, internal error messages, VO validation rules

Test Infrastructure

// tests/common/mod.rs — per-service helpers
pub async fn test_db() -> TestDb {
    TestDb::start("./migrations").await
}
pub fn test_app_state(pool: PgPool) -> AppState {
    AppState::new_with_jwt(pool, test_auth_config())
}

Container sharing and test utilities (TestDb, TestRedis, TestKafka, TestConsumer) are documented in shared/CLAUDE.md.

Event Integration — Outbox + Kafka

Infra: Shared TestDb + TestKafka Test: full relay cycle (insert → claim → publish → consume), payload fidelity through Kafka, per-aggregate ordering, consumer idempotency, delete-on-publish mode, retry-then-publish See: shared/CLAUDE.md for outbox + Kafka API examples

Order for New Services

Value object unit tests (fast feedback, no infra)
Router tests for all endpoints (canonical happy-path + HTTP contract)
Service tests only for auth guards and business rules
Repository tests only for SQL-specific concerns
Event integration tests for services that publish domain events
Verify no test duplicates an assertion at another layer