22. Testing with node:test

Since Node 18+, `node:test` provides a built-in test runner with `test()`, `describe()`/`it()`, and an `assert` module, runnable via `node --test`.

js
import { test } from "node:test";
import assert from "node:assert/strict";

function add(a, b) { return a + b; }

test("add sums two numbers", () => {
  assert.equal(add(2, 3), 5);
});

test("add handles negatives", () => {
  assert.equal(add(-1, 1), 0);
});

Running `node --test` auto-discovers files matching common test naming patterns (`*.test.js`) and reports pass/fail with a TAP-compatible summary — useful for small projects that want tests without adding Jest or Vitest as a dependency.

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