Neutrino Mocha Preset

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neutrino-preset-mocha is a Neutrino preset that supports testing JavaScript projects with the Mocha 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 v6.10+
  • Yarn or npm client
  • Neutrino v6, Neutrino build preset

Installation

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

Yarn

❯ yarn add --dev neutrino-preset-mocha

npm

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

Project Layout

neutrino-preset-mocha 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 _test.js by default.

Quickstart

After adding the Mocha 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:

import assert from 'assert';

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

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 --use neutrino-preset-node neutrino-preset-mocha"
  }
}

Or if you are using .neutrinorc.js, add this preset to your use array instead of --use flags:

module.exports = {
  use: [
    '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';

For more details on specific Mocha usage, please refer to their documentation.

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.

Preset options

You can provide custom options and have them merged with this preset's default options, which are subsequently passed to Mocha. You can modify Mocha settings from .neutrinorc.js by overriding with any options Mocha accepts. In a standalone Mocha project this is typically done from a mocha.opts file, but neutrino-preset-mocha allows configuration through .neutrinorc.js. This accepts the same options specified by Mocha defined on the Mocha documentation site, with command-line flags mapping to camel-cased options. Use an array pair instead of a string to supply these options in .neutrinorc.js.

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

module.exports = {
  use: [
    ['neutrino-preset-mocha', { reporter: 'nyan' }]
  ]
};
❯ yarn test

 1   -__,------,
 0   -__|  /\_/\
 0   -_~|_( ^ .^)
     -_ ""  ""

  1 passing (362ms)

✨  Done in 3.28s.

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:

Name Description Environments
compile Compiles JS files from the test directory using adopted Babel settings from other build presets. Contains a single loader named babel. all

Override configuration

By following the customization guide and knowing the rule, and loader IDs above, you can override and augment testing by providing a function to your .neutrinorc.js use array. You can also make this change from the Neutrino API when using the use method.

In a standalone Mocha project this is typically done in a mocha.opts file, but neutrino-preset-mocha allows configuration through .neutrinorc.js. This accepts the same options specified by Mocha defined on the Mocha documentation site, with command-line flags mapping to camel-cased options. Use an array pair instead of a string to supply these options.

Example: Add a custom Babel plugin when testing:

module.exports = {
  use: [
    'neutrino-preset-mocha'
  ],
  env: {
    NODE_ENV: {
      test: (neutrino) => neutrino.config.module
        .rule('compile')
        .use('babel')
        .tap(options => merge(options, {
          env: {
            test: {
              plugins: ['custom-babel-plugin']
            }
          }
        }))
    }
  }
};

Contributing

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

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