README

jest-config-base

MOXY's Jest base configuration.

Installation

$ npm install --save-dev jest @moxy/eslint-config-base

How it works

baseConfig is the base point of this configuration. It includes all defaults offered by jest-config and has project-agnostic configurations, meant to help any project regardless of their purpose, including:

Test match: Tweaks testMatch so that only files named test.js or files ending with .test.js are considered test files, even if they are inside __tests__ or any other folder.
Test path ignore patterns: Tweaks testPathIgnorePatterns to ignore common folders, such as docusaurus.
Transform:
- Enables Babel so that jest.mock() and similar functions are automatically hoisted to the top. If your project uses Babel, its configuration will be read and used to transpile code.
- Setups transforms for common files, such as images and files.
Coverage: Enables coverage for CI, a feature supported by ci-info, which you can check for information about supported CI services.
Coverage thresholds: For a good balance between strict but workable thresholds.
Snapshot serializing: To remove absolute paths from your snapshots, reducing conflicts in CI.

Usage

Create jest.config.js at the root of your project:

'use strict';

const { baseConfig } = require('@moxy/jest-config-base');

module.exports = baseConfig();

The baseConfig function accepts an optional parameter that allows to specify the Jest environment, which can be jsdom (default) or node. As an example, for Node.js projects you would use like so:

const { baseConfig } = require('@moxy/jest-config');

module.exports = baseConfig('node');

Alternatively, you may pass a path to a custom environment. In fact, we offer the following custom environments:

@moxy/jest-config/environments/node-single-context

Special Node environment class for Jest which runs all scripts in the same context. This effectively disables the sandbox isolation to circumvent issues with Jest's sandboxing, which causes subtle bugs in specific situations, such as in code that relies in instanceof checks.

'use strict';

const { baseConfig } = require('@moxy/jest-config');

module.exports = baseConfig('@moxy/jest-config/environments/node-single-context');

⚠️ Only activate this environment if you are having problems with the aforementioned issue, and before trying other workarounds.

Composing enhancers

To use enhancers, use the compose function that comes with this package. Keep in mind, the first item should always be the base configuration! Here's an example of using compose:

'use strict';

const { compose, baseConfig } = require('@moxy/jest-config-base');
const withMyEnhancer = require('<your-own-enhancer>');

module.exports = compose(
    baseConfig(),
    withMyEnhancer(),
);

Enhancers are functions which accept a single argument, i.e., Jest's config object, and return the enhanced config. You may also use compose to add your own inline enhancer:

'use strict';

const { compose, baseConfig } = require('@moxy/jest-config');

module.exports = compose(
    baseConfig(),
    (config) => ({
        ...config,
        // Do not test `.data.js` files
        testPathIgnorePatterns: [
            ...config.pathIgnorePatterns,
            '/.*.data.js$/'
        ];
    }),
);

Without compose

If you want to modify the base config without using compose, you may change the config imperatively like so:

'use strict';

const { baseConfig } = require('@moxy/jest-config');

const config = baseConfig();

// Do not test `.data.js` files
config.testPathIgnorePatterns = [
    ...config.testPathIgnorePatterns,
    '/.*.data.js$/'
];

module.exports = config;

Tests

Any parameter passed to the test command is passed down to Jest.

$ npm t
$ npm t -- --watch  # To run watch mode

Usage no npm install needed!