Karma-jest NPM

karma-jest

A Karma framework for using some of Jest's best features in a browser.

Install

npm i karma-jest -D

Or with yarn

yarn add karma-jest -D

Usage

In your karma config:

module.exports = config => {
  config.set({
    // add your test files
    files: ['test/**/*.test.js'],

    plugins: ['karma-jest'],
    frameworks: ['jest'],
    reporters: ['jest'],

    // Add options
    jest: {
      snapshotPath: 'test/__snapshots__',
    },
  });
};

Options

At the momement there is only one option:

snapshotPath: the directory snapshots are saved in, defaults to: path.join(karmaConfig.basePath, '__snapshots__')

Differences from Jest

Because a browser is very different environment from Node, there are a few key differences with how karma-jest works compared to Jest.

Compiling and bundling test files is up to you. Use which ever karam preprocessor is appropriate for your project, probably karma-webpack or karma-preprocessor-rollup.
Test's are organized by top level describe blocks instead of test files. this means .only tests apply to the entire test suite, and snapshots are located in a single directory organized by suite name, instead of file name.
module mocking does not work! You can use something specific to your preprocessor if you need.