A simple yet powerful testing framework for Node.js

Japa comes with everything you need to test your backend applications. Be it writing JSON API tests using an Open API schema or writing browser tests using Playwright.

Unlike other testing frameworks born out of the frontend ecosystem, Japa focuses only on testing backend applications and libraries. Therefore, Japa is simpler, faster, and bloatware free.

Japa installation size is 9 times smaller than Vitest and 5 times smaller than Jest.

While smaller bundle size should not be a factor for choosing a framework, it does indicate the frontend first test runners bundles dependencies that are not relevant when developing strictly for Node.js.

No overhead of transpiling source code

Popular testing frameworks like Jest (uses Babel) and Vitest (uses Vite) use transpilers to process your source code. No matter how quick the underlying transpilers are, they will always have additional overhead compared to tools with no transpilers.

If you are building libraries or applications to work with Node.js runtime (not the browser), there is no need to use a transpiler. As a result:

  • You will have a better debugging experience.
  • Your application and tests will boot faster.
  • No additional configuration to manage.

Works with your existing project setup

Since Japa does not have to use transpilers, it works with your existing project setup. Moreover, Japa does not even have a CLI tool. You run your tests using the node or bun command.

  • Got an ESM project? - Install Japa, create an entry point file, and you are good to go.
  • Got a TypeScript project? - Install Japa, create an entry point file, and use your existing TypeScript tooling like ts-node or tsx to run tests.
# Node.js
node bin/tests.js
# Bun
bun bin/tests.js
# TypeScript and TS Node
node --loader=ts-node/esm bin/tests.js
# TypeScript with TSX
npx tsx bin/tests.js

What else does Japa have to offer?

Japa ticks almost every checkbox to provide a great testing experience, ships with a ton of officially maintained plugins and a VSCode extension to view and run tests directly from your code editor.

  • Support for asynchronous tests.
  • Support for snapshot testing.
  • Official plugins for chai assert and jest expect assertion libraries.
  • Coverage reporting using nyc and c8.
  • Ability to pin and run only selected tests.
  • Organize tests inside multiple test suites and groups.

Basics covered

Despite being a small and simple test runner, Japa comes with all the basic features you expect from a great testing framework.

  • Register an Open API schema.
  • Make an HTTP request to your API server.
  • Assert the response body, headers, and status code matches the schema structure.

JSON API testing using Open API schema

The API client plugin of Japa has first-class support for testing API endpoints against an Open API schema.

  • Automatic management of browser and browser context.
  • Class-based pages and interactions to de-compose tests into small testable units.
  • Web first assertions.
  • Control headless mode, debugging, and enable tracing using command-line flags.

Browser testing using Playwright

The browser client of Japa is built on top of Playwright and you can use it to write end-to-end browser tests.

test('validate email')
.run(({ assert }, email) => {

Dataset driven tests

Datasets allow you to test a function output against varying inputs.

VSCode extension

Run Japa tests directly from your code editor using our VSCode extension.