jest

Run all available tests

$ jest

$ jest [path/to/file1 path/to/file2 ...]

$ jest [regex1 regex2 ...]

$ jest --testNamePattern [regex]

$ jest --findRelatedTests [path/to/source_file.js]

$ jest --onlyChanged

$ jest --watch

$ jest --help

jest [options] [<file|directory|pattern> …]

--watch
    Watch files for changes and rerun tests related to changed files

--watchAll
    Watch files for changes and rerun all tests

--coverage
    Indicates whether coverage information should be collected

--ci
    Run in CI mode (similar to --no-interactive --no-watchman)

--config
    Path to Jest config file

--init
    Initialize Jest configuration

--clearCache
    Clear Jest's cache

--debug
    Print additional debug information

--silent
    Prevent tests from outputting messages to console

--verbose
    Display individual test results

--runInBand
    Run tests serially in current process

--updateSnapshot
    Update failing snapshots

--testNamePattern
    Run tests with matching name using regex

--testPathPattern
    Run tests located in matching paths

--bail
    Exit after first test failure

Jest is a delightful JavaScript Testing Framework with a focus on simplicity and developer experience. Developed by Facebook (now Meta), it provides instant feedback with zero configuration for most projects. It supports testing for React, Node.js, TypeScript, Babel, Vue, Angular, and more.

Jest runs tests in parallel by default, offers snapshot testing, code coverage reports, mocking capabilities, and a built-in assertion library powered by Jasmine. On Linux, it's typically installed via npm or yarn as a dev dependency and invoked from Node.js projects.

Key strengths include watch mode for rapid iteration, automatic test environment setup, and robust matching utilities. It's widely used in modern web development for unit, integration, and end-to-end testing, making it faster and more reliable than traditional runners like Mocha.

Requires Node.js (≥14); not a native Linux binary—instantiate via npm/yarn. Large projects may need config tweaks for performance. Cache issues can occur across Node versions.

npm install --save-dev jest
or yarn add --dev jest
Add to package.json: "test": "jest"

Uses jest.config.js or package.json. Key options: testEnvironment, testMatch, collectCoverageFrom, moduleNameMapping.
Run jest --init for guided setup.

Created by Facebook in 2014 as a React testing solution; open-sourced and evolved into a general JS framework. Version 1.0 in 2014; now at v29+ maintained by the Jest community post-Facebook handover in 2020.

node(1), npm(1), yarn(1)