jest-dev-server

What is jest-dev-server?

The jest-dev-server package is a utility for running a development server while running Jest tests. It is particularly useful for end-to-end (E2E) testing where you need a server to be up and running before executing your tests.

What are jest-dev-server's main functionalities?

Starting a development server

This feature allows you to start a development server before running your tests. The `setupDevServer` function takes an object with a `command` to start the server and a `port` to listen on.

const { setup: setupDevServer } = require('jest-dev-server');

beforeAll(async () => {
  await setupDevServer({
    command: 'npm run start',
    port: 3000,
  });
});

Stopping the development server

This feature allows you to stop the development server after your tests have completed. The `teardownDevServer` function ensures that the server is properly shut down.

const { teardown: teardownDevServer } = require('jest-dev-server');

afterAll(async () => {
  await teardownDevServer();
});

Custom server options

This feature allows you to customize the server options such as `launchTimeout` and `debug` mode. This is useful for fine-tuning the server startup process to match your specific needs.

const { setup: setupDevServer } = require('jest-dev-server');

beforeAll(async () => {
  await setupDevServer({
    command: 'npm run start',
    port: 3000,
    launchTimeout: 50000,
    debug: true,
  });
});

Other packages similar to jest-dev-server

start-server-and-test

The start-server-and-test package is another utility for starting a server and running tests. It is more versatile as it can be used with any test runner, not just Jest. It also provides more flexibility in terms of waiting for the server to be ready before running tests.

wait-on

The wait-on package is a utility that waits for files, ports, sockets, and http(s) resources to become available. It can be used in conjunction with other tools to ensure that a server is up and running before executing tests. It is more general-purpose compared to jest-dev-server.

concurrently

The concurrently package allows you to run multiple commands concurrently. It can be used to start a server and run tests in parallel. While it does not provide the same level of integration with Jest as jest-dev-server, it is a powerful tool for managing multiple processes.

README

jest-dev-server

Starts a server before your Jest tests and tears it down after.

Why

jest-puppeteer works great for running tests in Jest using Puppeteer. It's also useful for starting a local development server during the tests without letting Jest hang. This package extracts just the local development server spawning without any ties to Puppeteer.

Install

npm install --save-dev jest-dev-server

Usage

jest-dev-server exports setup,teardown and getServers functions.

// global-setup.js
const { setup: setupDevServer } = require('jest-dev-server')

module.exports = async function globalSetup() {
  await setupDevServer({
    command: `node config/start.js --port=3000`,
    launchTimeout: 50000,
    port: 3000,
  })
  // Your global setup
}

It is also possible to specify several servers:

// global-setup.js
const { setup: setupDevServer } = require('jest-dev-server')

module.exports = async function globalSetup() {
  await setupDevServer([
    {
      command: 'node server.js',
      port: 4444,
    },
    {
      command: 'node server2.js',
      port: 4445,
    },
  ])
  // Your global setup
}

// global-setup.js
const { setup: setupDevServer, getServers } = require('jest-dev-server')

module.exports = async function globalSetup() {
  await setupDevServer({
    command: `node config/start.js --port=3000`,
    launchTimeout: 50000,
    port: 3000,
  })
  getServers.then((servers) => {
    // You can get to the servers and do whatever you want
  })
  // Your global setup
}

// global-teardown.js
const { teardown: teardownDevServer } = require('jest-dev-server')

module.exports = async function globalTeardown() {
  await teardownDevServer()
  // Your global teardown
}

Options

command

Type: string, required.

Command to execute to start the port. Directly passed to spawnd.

module.exports = {
  command: 'npm run start',
}

debug

Type: boolean, default to false.

Log server output, useful if server is crashing at start.

module.exports = {
  command: 'npm run start',
  debug: true,
}

launchTimeout

Type: number, default to 5000.

How many milliseconds to wait for the spawned server to be available before giving up. Defaults to wait-port's default.

module.exports = {
  command: 'npm run start',
  launchTimeout: 30000,
}

---

Following options are linked to spawnd.

host

Type: string, default to localhost.

Host to wait for activity on before considering the server running. Must be used in conjunction with port.

module.exports = {
  command: 'npm run start --port 3000',
  host: 'customhost.com',
  port: 3000,
}

path

Type: string, default to null.

Path to resource to wait for activity on before considering the server running. Must be used in conjunction with host and port.

module.exports = {
  command: 'npm run start --port 3000',
  host: 'customhost.com',
  port: 3000,
  path: 'thing',
}

protocol

Type: string, (https, http, tcp, socket) default to tcp.

To wait for an HTTP or TCP endpoint before considering the server running, include http or tcp as a protocol. Must be used in conjunction with port.

module.exports = {
  command: 'npm run start --port 3000',
  protocol: 'http',
  port: 3000,
}

port

Type: number, default to null.

Port to wait for activity on before considering the server running. If not provided, the server is assumed to immediately be running.

module.exports = {
  command: 'npm run start --port 3000',
  port: 3000,
}

usedPortAction

Type: string (ask, error, ignore, kill) default to ask.

It defines the action to take if port is already used:

• ask: a prompt is shown to decide if you want to kill the process or not
• error: an errow is thrown
• ignore: your test are executed, we assume that the server is already started
• kill: the process is automatically killed without a prompt

module.exports = {
  command: 'npm run start --port 3000',
  port: 3000,
  usedPortAction: 'kill',
}

waitOnScheme

jest-dev-server use the wait-on npm package to wait for resources to become available before calling callback.

Type: object, default to {}.

• delay: optional initial delay in ms, default 0
• interval: optional poll resource interval in ms, default 250ms
• log: optional flag which outputs to stdout, remaining resources waited on and when complete or errored
• reverse: optional flag to reverse operation so checks are for resources being NOT available, default false
• timeout: optional timeout in ms, default Infinity. Aborts with error
• tcpTimeout: optional tcp timeout in ms, default 300ms
• verbose: optional flag which outputs debug output, default false
• window: optional stabilization time in ms, default 750ms. Waits this amount of time for file sizes to stabilize or other resource availability to remain unchanged

Note: http(s) specific options, see https://github.com/request/request#readme for specific details

module.exports = {
  command: 'npm run start --port 3000',
  port: 3000,
  usedPortAction: 'kill',
  waitOnScheme: {
    delay: 1000,
  },
}

Troubleshooting

• If using port makes the terminal to ask for root password although the port is valid and accessible then use usePortAction: 'ignore'.

License

MIT

Changelog

6.0.3 (2021-12-14)

Bug Fixes

• avoid running connect in global setup if browserWSEndpoint provided in config (#458) (c9fa515)