Even though JavaScript is single-threaded, IO in Node.js can happen in parallel due to its async nature. AVA takes advantage of this and runs your tests concurrently, which is especially beneficial for IO heavy tests. In addition, test files are run in parallel as separate processes, giving you even better performance and an isolated environment for each test file. Switching from Mocha to AVA in Pageres brought the test time down from 31 sec to 11 sec. Having tests run concurrently forces you to write atomic tests, meaning tests don't depend on global state or the state of other tests, which is a great thing!

Code Quality Rank: L4
Monthly Downloads: 0
Programming language: JavaScript
License: MIT License
Tags: Testing Frameworks     Assertion     Runner     Testing     Generator     Babel     Automation     Concurrency     TypeScript     Await     Async     Promises     Promise     Flow     CLI     Fast     Tap     TDD     Test     Mocha     Parallel     Observable     Concurrent     Tape     Unit     Jasmine     QUnit     Assert     Observables     Yield     Generators     Function     Futuristic     Cli-app     Ava     Jest     Expect     Snapshot     🦄    
Latest version: v2.4.0

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Build Status Coverage Status XO code style Join the community on Spectrum Mentioned in Awesome Node.js

Testing can be a drag. AVA helps you get it done. AVA is a test runner for Node.js with a concise API, detailed error output, embrace of new language features and process isolation that let you write tests more effectively. So you can ship more awesome code. 🚀

Follow the AVA Twitter account for updates.

Read our [contributing guide](contributing.md) if you're looking to contribute (issues / PRs / etc).


Translations: Español, Français, Italiano, 日本語, 한국어, Português, Русский, 简体中文

Why AVA?

  • Minimal and fast
  • Simple test syntax
  • Runs tests concurrently
  • Enforces writing atomic tests
  • No implicit globals
  • Includes TypeScript definitions
  • Magic assert
  • [Isolated environment for each test file](./docs/01-writing-tests.md#process-isolation)
  • Write your tests using the latest JavaScript syntax
  • [Promise support](./docs/01-writing-tests.md#promise-support)
  • [Async function support](./docs/01-writing-tests.md#async-function-support)
  • [Observable support](./docs/01-writing-tests.md#observable-support)
  • [Enhanced assertion messages](./docs/03-assertions.md#enhanced-assertion-messages)
  • Automatic parallel test runs in CI
  • [TAP reporter](./docs/05-command-line.md#tap-reporter)


To install and set up AVA, run:

npm init ava

Your package.json will then look like this (exact version notwithstanding):

    "name": "awesome-package",
    "scripts": {
        "test": "ava"
    "devDependencies": {
        "ava": "^1.0.0"

Or if you prefer using Yarn:

yarn add ava --dev

Alternatively you can install ava manually:

npm install --save-dev ava

Don't forget to configure the test script in your package.json as per above.

Create your test file

Create a file named test.js in the project root directory:

import test from 'ava';

test('foo', t => {

test('bar', async t => {
    const bar = Promise.resolve('bar');
    t.is(await bar, 'bar');

Running your tests

npm test

Or with npx:

npx ava

Run with the --watch flag to enable AVA's [watch mode](docs/recipes/watch-mode.md):

npx ava --watch

Supported Node.js versions

AVA supports the latest release of any major version that is supported by Node.js itself. Read more in our [support statement](docs/support-statement.md).


Magic assert

AVA adds code excerpts and clean diffs for actual and expected values. If values in the assertion are objects or arrays, only a diff is displayed, to remove the noise and focus on the problem. The diff is syntax-highlighted too! If you are comparing strings, both single and multi line, AVA displays a different kind of output, highlighting the added or missing characters.


Clean stack traces

AVA automatically removes unrelated lines in stack traces, allowing you to find the source of an error much faster, as seen above.

Latest JavaScript support

AVA uses Babel 7 so you can use the latest JavaScript syntax in your tests. There is no extra setup required. You don't need to be using Babel in your own project for this to work either.

We aim to support all finished syntax proposals, as well as all syntax from ratified JavaScript versions (e.g. ES2017). See our @ava/stage-4 preset for the currently supported proposals.

Please note that we do not add or modify built-ins. For example, if you use Object.fromEntries() in your tests, they will crash in Node.js 10 which does not implement this method.

You can disable this syntax support, or otherwise customize AVA's Babel pipeline. See our [Babel recipe] for more details.

Parallel runs in CI

AVA automatically detects whether your CI environment supports parallel builds. Each build will run a subset of all test files, while still making sure all tests get executed. See the ci-parallel-vars package for a list of supported CI environments.


Please see the [files in the docs directory](./docs):

  • [Writing tests](./docs/01-writing-tests.md)
  • [Execution context](./docs/02-execution-context.md)
  • [Assertions](./docs/03-assertions.md)
  • [Snapshot testing](./docs/04-snapshot-testing.md)
  • [Command line (CLI)](./docs/05-command-line.md)
  • [Configuration](./docs/06-configuration.md)
  • [Test timeouts](./docs/07-test-timeouts.md)

Common pitfalls

We have a growing list of [common pitfalls](docs/08-common-pitfalls.md) you may experience while using AVA. If you encounter any issues you think are common, comment in this issue.


  • [Test setup](docs/recipes/test-setup.md)
  • [Code coverage](docs/recipes/code-coverage.md)
  • [Watch mode](docs/recipes/watch-mode.md)
  • [Endpoint testing](docs/recipes/endpoint-testing.md)
  • [When to use t.plan()](docs/recipes/when-to-use-plan.md)
  • [Browser testing](docs/recipes/browser-testing.md)
  • [TypeScript](docs/recipes/typescript.md)
  • [Flow](docs/recipes/flow.md)
  • [Configuring Babel][Babel recipe]
  • [Using ES modules](docs/recipes/es-modules.md)
  • [Passing arguments to your test files](docs/recipes/passing-arguments-to-your-test-files.md)
  • [Testing React components](docs/recipes/react.md)
  • [Testing Vue.js components](docs/recipes/vue.md)
  • [JSPM and SystemJS](docs/recipes/jspm-systemjs.md)
  • [Debugging tests with Chrome DevTools](docs/recipes/debugging-with-chrome-devtools.md)
  • [Debugging tests with VSCode](docs/recipes/debugging-with-vscode.md)
  • [Debugging tests with WebStorm](docs/recipes/debugging-with-webstorm.md)
  • [Isolated MongoDB integration tests](docs/recipes/isolated-mongodb-integration-tests.md)
  • [Testing web apps using Puppeteer](docs/recipes/puppeteer.md)


Why not mocha, tape, tap?

Mocha requires you to use implicit globals like describe and it with the default interface (which most people use). It's not very opinionated and executes tests serially without process isolation, making it slow.

Tape and tap are pretty good. AVA is highly inspired by their syntax. They too execute tests serially. Their default TAP output isn't very user-friendly though so you always end up using an external tap reporter.

In contrast AVA is highly opinionated and runs tests concurrently, with a separate process for each test file. Its default reporter is easy on the eyes and yet AVA still supports TAP output through a CLI flag.

How is the name written and pronounced?

AVA, not Ava or ava. Pronounced [/ˈeɪvə/](media/pronunciation.m4a?raw=true): Ay (f*ace, made) V (vie, have) A (comma, **a*go)

What is the header background?

It's the Andromeda galaxy.

What is the difference between concurrency and parallelism?

Concurrency is not parallelism. It enables parallelism.



Mark Wubben Sindre Sorhus Vadim Demedes
Mark Wubben Sindre Sorhus Vadim Demedes