AVA - Node.js Test Runner That Actually Works

I switched to AVA after Jest's memory usage killed our CI and tests kept mysteriously failing when run together. AVA fixes the biggest problem with JavaScript testing: test pollution.

Process Isolation Actually Works

Each test file runs in its own Node.js child process. This means:

• No shared state between tests that causes random failures
• Tests can't accidentally modify global objects and break other tests
• Memory leaks in one test file don't affect others
• You can run tests in any order without weird interactions

Jest claims to isolate tests but still runs them in the same process with worker threads. I've seen Jest tests pass individually but fail when run together because some test modified process.env or a global variable. AVA goes full nuclear and spawns separate processes. Yeah, it uses more memory, but it actually works.

Error Messages Don't Make You Want To Quit

When AVA tests fail, you get:

• Clean diffs showing exactly what's different
• Code excerpts with syntax highlighting
• No stack trace pollution from framework internals
• Line numbers that actually point to your failing code

Compare this to Mocha's verbose wall of text or Jest's stack traces where half the output is framework bullshit. AVA uses power-assert under the hood to provide meaningful failure output.

ES Modules Just Work

AVA was built for modern JavaScript from day one. No babel configuration hell, no "type": "module" dance in package.json. Import your modules and AVA handles the rest.

import test from 'ava';
import { myFunction } from '../src/utils.js';

test('myFunction works', t => {
    t.is(myFunction(), 'expected result');
});

AVA's native ESM support means you can use dynamic imports, top-level await, and other modern features without transpilation.

The Downsides Nobody Mentions

• Higher memory usage because of process isolation
• Slower startup time (each process needs to boot Node.js)
• No built-in browser testing - it's Node.js only
• Smaller ecosystem compared to Jest's massive plugin library
• Learning curve if you're used to globals like describe() and it()

But if you have a large test suite that's been flaky or slow, AVA's process isolation is worth the tradeoffs.

Installation That Actually Works

npm init ava

That's it. This npm init command does everything you need:

• Installs AVA as a dev dependency
• Sets up the test script in package.json
• Configures ES modules (no more import/require headaches)
• Creates an example test file following AVA's conventions

If you prefer doing it manually:

npm install --save-dev ava

Then add this to your package.json:

{
  "scripts": {
    "test": "ava"
  },
  "type": "module"
}

Your First Test (That Won't Fail Mysteriously)

Create test.js and write something simple:

import test from 'ava';

test('math still works', t => {
    t.is(2 + 2, 4);
});

test('async code without the pain', async t => {
    const response = await fetch('https://api.example.com/status');
    const data = await response.json();
    t.truthy(data.ok);
});

Run it:

npm test

Version Info That Matters

As of September 2025, AVA is at version 6.4.1 (released July 12, 2025). Works on Node 18+, use Node 20 LTS for production.

Check your Node version with node --version.

Common Setup Issues You'll Hit

ES Modules Error: If you see SyntaxError: Cannot use import statement outside a module, make sure you have "type": "module" in your package.json. This bit me for 2 hours on my first AVA project.

TypeScript Issues: Install @ava/typescript if you want TypeScript support:

npm install --save-dev @ava/typescript

Windows Process Limits: AVA spawns lots of processes. On Windows, you might hit process limits with large test suites. I learned this the hard way when our 300-test suite crashed Windows with "EMFILE: too many open files". Set concurrency lower:

ava --concurrency=2

Who Actually Uses This Thing

Real projects using AVA (not just demo repos):

• Sindre Sorhus's 1000+ npm packages (he created AVA, so obviously)
• Got HTTP client - 14k GitHub stars, solid choice for API calls
• Electron's build tools - yeah, the desktop app framework
• XO linter - opinionated ESLint config that actually works
• p-queue - Promise-based queue with concurrency control
• np - Better npm publish experience

About 500k weekly downloads, which is decent but nowhere near Jest's 20M+. Smaller community means fewer Stack Overflow answers but also less noise.