Jest

Configuration Commands

Configure Jest for your project with jest.config.ts, setup files, module mappers, and transform settings. Properly configured Jest makes testing fast and reliable.

8 commands

Pro Tips

Use 'jest --init' to generate a starter config file with guided prompts for your project type.

Map path aliases with 'moduleNameMapper': { '^@/(.*)': '<rootDir>/src/$1' } to match your tsconfig paths.

Use 'projects' in jest config to run different configurations (e.g., unit and integration) in a single command.

Common Mistakes

Avoid 'transformIgnorePatterns' that exclude node_modules you need transformed. ESM packages often need transformation.

Setting 'testEnvironment: jsdom' for all tests slows Node.js-only tests. Use per-file docblocks: /** @jest-environment node */.

Commands

Custom config

$ jest -c jest.custom.config.js

Run with custom config file.

Config file option

$ jest --config jest.config.js

Specify configuration file path.

Silent mode

$ jest --silent

Suppress all console output.

Node environment

$ jest --env node

Use Node environment instead of jsdom.

Set max workers

$ jest --maxWorkers=4

Limit number of worker processes.

Serial execution shorthand

$ jest -i

Run tests serially (shorthand).

Detect open handles

$ jest --detectOpenHandles

Find async operations that prevent exit.

Force exit

$ jest --forceExit

Force Jest to exit after tests complete.