neutrino-dev/docs/presets/neutrino-preset-jest

Neutrino Jest Preset

neutrino-preset-jest is a Neutrino preset that supports testing JavaScript projects with the Jest test runner.

Features

• Zero upfront configuration necessary to start testing
• Babel compilation that compiles your tests using the same Babel options used by your source code
• Easily extensible to customize your testing as needed

Requirements

• Node.js v6.9+
• Yarn or npm client
• Neutrino v4, Neutrino build preset

Installation

neutrino-preset-jest can be installed via the Yarn or npm clients. Inside your project, make sure neutrino and neutrino-preset-jest are development dependencies. You will also be using another Neutrino preset for building your application source code.

Yarn

❯ yarn add --dev neutrino-preset-jest

npm

❯ npm install --save-dev neutrino-preset-mocha

Project Layout

neutrino-preset-jest follows the standard project layout specified by Neutrino. This means that by default all project test code should live in a directory named test in the root of the project. Test files end in either _test.js or .test.js.

Quickstart

After adding the Jest preset to your Neutrino-built project, add a new directory named test in the root of the project, with a single JS file named simple_test.js in it.

❯ mkdir test && touch test/simple_test.js

Edit your test/simple_test.js file with the following:

describe('simple', () => {
  it('should be sane', () => {
    expect(!false).toBe(true);
  });
});

Now edit your project's package.json to add commands for testing your application. In this example, let's pretend this is a Node.js project:

{
  "scripts": {
    "test": "neutrino test --presets neutrino-preset-node neutrino-preset-mocha"
  }
}

Run the tests, and view the results in your console:

Yarn

❯ yarn test

  simple
    ✓ should be sane


  1 passing (426ms)

✨  Done in 4.17s.

npm

❯ npm test

  simple
    ✓ should be sane


  1 passing (409ms)

To run tests against files from your source code, simply import them:

import thingToTest from '../src/thing';

Executing single tests

By default this preset will execute every test file located in your test directory ending in _test.js. Use the command line files parameters to execute individual tests.

Customizing

To override the test configuration, start with the documentation on customization. neutrino-preset-mocha creates some conventions to make overriding the configuration easier once you are ready to make changes.

Rules

The following is a list of rules and their identifiers which can be overridden:

• compile: Compiles JS files from the test directory using Babel. Contains a single loader named babel.

Simple customization

By following the customization guide and knowing the rule, loader, and plugin IDs above, you can override and augment the build directly from package.json.

Advanced configuration

By following the customization guide and knowing the rule, and loader IDs above, you can override and augment testing by creating a JS module which overrides the config.

You can modify Mocha settings by overriding the preset with any options Mocha accepts. This is stored in the neutrino.custom.mocha object.

Example: Switch the test reporter from the default spec to nyan:

module.exports = neutrino => {
  neutrino.custom.mocha.reporter = 'nyan';
};

❯ yarn test
yarn test v0.19.1
$ node_modules/neutrino/bin/neutrino test
 1   -__,------,
 0   -__|  /\_/\
 0   -_~|_( ^ .^)
     -_ ""  ""

  1 passing (362ms)

✨  Done in 3.28s.

Contributing

This preset is part of the neutrino-dev repository, a monorepo containing all resources for developing Neutrino and its core presets. Follow the contributing guide for details.