Testing with node:test

The built-in test runner

Since Node 20 the test runner is stable. Import test from node:test and use node:assert for checks.

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

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

test("async works", async () => {
  const data = await Promise.resolve(42);
  assert.equal(data, 42);
});

Run all test files, watch for changes and collect coverage.

node --test
node --test --watch
node --test --experimental-test-coverage

Keep tests small and independent, name them after the behaviour, and run them in CI on every push.

Quick check

Quick check: Which command runs Node's built-in tests?

• node --test
• npm install test
• node --check
• node --lint