The **arrange‑act‑assert (AAA)** library is a zero‑dependency testing framework for Node/TypeScript that structures tests around explicit **ARRANGE**, **ACT**, and **ASSERT** phases (with optional multiple assertions, snapshots, and after‑hooks). It provides a simple API (`test`, `describe`, CLI `aaa`) for writing isolated, composable unit tests, supports parallel execution, code‑coverage, snapshot testing, and can be used programmatically via `TestSuite`. It is aimed at developers who want a lightweight, opinionated alternative to larger test runners and prefer the AAA pattern for clearer test organization.