Testing conventions and in-memory databases

When to use: Writing or debugging tests, choosing unit vs integration style, Postgres/ClickHouse tests, regenerating ClickHouse test schema, or exporting test helpers from packages without pulling test code into production bundles.

Package exports (test code isolation)

Test utilities (fakes, in-memory DB helpers, fixtures) must not be exported from a package’s main entry (src/index.ts).

• Never re-export from ./test/ or ./testing/ in the main src/index.ts
• To expose test helpers, add a /testing subpath in package.json exports:

{
  "exports": {
    ".": "./src/index.ts",
    "./testing": "./src/testing/my-test-helpers.ts"
  }
}

• Consumers: import { Fake } from "@platform/my-package/testing"
• Biome noRestrictedImports blocks test paths in production source; tsdown fails the build if test code is resolved from prod entry points

Conventions

• Shared default environment: Node with globals enabled (packages/vitest-config/index.ts)
• Write tests, mostly e2e, some unit tests when logic is complex
• Unit tests: domain entities/use-cases/policies with fakes
• Contract tests: adapter compliance against domain ports
• Integration tests: infra-backed tests for Postgres/ClickHouse/Redis/BullMQ/object storage
• End-to-end tests: ingest boundary to query boundary across organization scoping
• Keep tests deterministic and isolated
• Prefer package-local runs during iteration; run full monorepo tests before PR

Database testing (in-memory)

Always use in-memory databases for tests. Do not use vi.mock/vi.fn to mock repository methods and do not require running database servers. The project provides embedded, in-process database engines that run the real SQL against the real schema:

• ClickHouse → chdb (chdb package): An in-process ClickHouse engine via @platform/testkit.
• Postgres → PGlite (@electric-sql/pglite): An in-process Postgres via WASM via @platform/testkit.

Postgres test setup (@platform/testkit)

import { setupTestPostgres } from "@platform/testkit"
import { beforeAll, describe, it } from "vitest"

const pg = setupTestPostgres()

describe("MyRepository", () => {
  it("does something", async () => {
    // pg.postgresDb is a real Drizzle instance backed by PGlite in-memory
    // pg.db is the lower-level Drizzle/PGlite instance for direct queries
  })
})

setupTestPostgres() registers vitest hooks automatically:

• beforeAll: creates a PGlite instance, creates the latitude_app role, and runs all Drizzle migrations
• afterAll: closes the PGlite connection

ClickHouse test setup (@platform/testkit)

import { setupTestClickHouse } from "@platform/testkit"
import { beforeAll, describe, it } from "vitest"

const ch = setupTestClickHouse()

describe("MyRepository", () => {
  let repo: ReturnType<typeof createMyRepository>

  beforeAll(() => {
    repo = createMyRepository(ch.client)
  })

  it("does something", async () => {
    // ch.client is a real ClickHouseClient backed by chdb in-memory
  })
})

setupTestClickHouse() registers vitest hooks automatically:

• beforeAll: creates a chdb session and loads the schema from schema.sql
• beforeEach: truncates all tables for test isolation
• afterAll: destroys the session and cleans up temp files

After new ClickHouse migrations, regenerate the in-memory test schema (only if the user asked you to run migration-related commands — see database-clickhouse-weaviate):

pnpm --filter @platform/db-clickhouse ch:schema:dump

Why not vi.mock?

Mocking repositories with vi.fn() tests the wiring, not the queries. In-memory databases catch real bugs: wrong column names, broken argMax aggregations, incorrect GROUP BY clauses, and schema mismatches. They run quickly with zero external dependencies.