The Node.js Test Runner
📌 Covered in this chapter:
Unit Tests · Assertions · Test Suites · Test Hooks · Async Tests
Write unit tests using Node's built-in test runner (node:test) — no external testing framework required.
1The Node.js Test Runner — What You'll Learn
Write unit tests using Node's built-in test runner (node:test) — no external testing framework required.
Here's everything this chapter covers, in the order you'll learn it:
- What testing is and why it matters
- Unit tests
- Integration tests
- End-to-end tests (overview)
- Node's built-in test runner
- Organizing test files
- Assertions with node:assert
- Test suites (describe-like grouping)
- Test hooks (before/after)
- Mocking dependencies
- Testing async code
- Measuring test coverage
2Working Example
💻 Example: The Node.js Test Runner
JavaScript
▶ Run in Compiler
import test from "node:test";
import assert from "node:assert/strict";
test("addition works", () => {
assert.equal(2 + 3, 5);
});3Best Practices & Common Pitfalls
💡 Key things to remember:
- Run tests with `node --test` — no extra packages needed for basic unit testing since Node.js LTS ships node:test built in.
❓ Frequently Asked Questions (FAQ)
Q What's the most important thing to understand about the node.js test runner?
Focus on: Unit Tests · Assertions · Test Suites · Test Hooks · Async Tests. These are the core building blocks this chapter's examples are built around, and they show up repeatedly in later chapters of this course.
Q Do I need external npm packages for the node.js test runner?
Only where explicitly shown in the code examples above (like Express, Zod, or Socket.IO) — otherwise, this chapter relies entirely on Node.js's own built-in capabilities.