ADR 0005: @arachnejs/testing harness

• Status: Accepted
• Date: 2026-09-27
• Deciders: Arachne core

Context #

Packages need shared test helpers without pulling Playwright, Testcontainers, or DB drivers into every unit test.

Decision #

Phase 0 ships a thin @arachnejs/testing with:

1. createTestApp — boots @arachnejs/core modules and returns { app, container, bus, dispose } with automatic dispose.
2. factory — typed object factory with overrides and sequences.
3. tempDir — creates and cleans a temporary directory.
4. waitFor — polling helper for async conditions.
5. mockLogger — capturing Logger for assertions.

Later phases extend this package (DB fixtures, render helpers, Playwright fixtures) without breaking these primitives. Optional peer deps are declared when those helpers land.

Depends on @arachnejs/core only.

Alternatives considered #

1. Per-package ad-hoc helpers — duplication and drift.
2. Full harness in Phase 0 — premature; no server/DB yet.

Consequences #

• Unit tests across packages share one harness API.
• Coverage of testing helpers themselves is required (≥ 80%).