jest-watcher

What is jest-watcher?

The jest-watcher package is a part of the Jest ecosystem and is used to implement custom watch plugins for Jest. It provides an API to create plugins that can hook into Jest's watch mode, allowing developers to add custom watch behaviors to their test suites.

What are jest-watcher's main functionalities?

Custom Watch Plugins

This feature allows developers to create custom watch plugins that can react to file changes, determine if a test suite should run, and more. The code sample shows a basic structure of a custom watch plugin.

class MyCustomPlugin {
  apply(jestHooks) {
    jestHooks.onFileChange(({ projects }) => {
      console.log('Files changed:', projects[0].changedFiles);
    });
    jestHooks.shouldRunTestSuite(() => true);
  }
}

module.exports = MyCustomPlugin;

Interactive Watch Plugins

This feature allows the creation of interactive watch plugins that can provide custom interactive CLI interfaces during Jest's watch mode. The code sample demonstrates how to implement an interactive behavior that filters tests based on a pattern.

class MyInteractivePlugin {
  run(globalConfig, updateConfigAndRun) {
    // Implement interactive behavior here
    updateConfigAndRun({
      testNamePattern: 'pattern to filter tests'
    });
    return Promise.resolve();
  }
}

module.exports = MyInteractivePlugin;

Other packages similar to jest-watcher

mocha-watch

Mocha-watch is a watch mode for Mocha testing framework. It provides similar functionality to jest-watcher by re-running tests when file changes are detected. However, it is tailored for Mocha and does not offer the same plugin API for extending watch behavior.

karma

Karma is a test runner that works with multiple testing frameworks like Jasmine, Mocha, and QUnit. It can watch files and re-run tests on changes, similar to jest-watcher. Karma is more of a full-fledged test runner with a focus on running tests in different browsers, whereas jest-watcher is specifically for creating watch plugins in Jest.

ava

AVA is a test runner with built-in watch mode functionality. It automatically re-runs tests when it detects changes. AVA's watch mode is not plugin-based like jest-watcher, but it offers a simple and fast out-of-the-box solution for watching tests without the need for additional configuration.

README

The README file is missing

Changelog

29.7.0

Features

• [create-jest] Add npm init / yarn create initialiser for Jest projects (#14465)
• [jest-validate] Allow deprecation warnings for unknown options (#14499)

Fixes

• [jest-resolver] Replace unmatched capture groups in moduleNameMapper with empty string instead of undefined (#14507)
• [jest-snapshot] Allow for strings as well as template literals in inline snapshots (#14465)
• [@jest/test-sequencer] Calculate test runtime if perStats.duration is missing (#14473)

Performance

• [@jest/create-cache-key-function] Cache access of NODE_ENV and BABEL_ENV (#14455)

Chore & Maintenance

• [jest-cli] Move internal config initialisation logic to the create-jest package (#14465)