@nrwl/jest

What is @nrwl/jest?

The @nrwl/jest package is part of the Nx suite of tools, designed to enhance the development experience with Jest in a monorepo setup. It provides seamless integration of Jest into Nx workspaces, enabling efficient unit testing configurations, execution, and optimizations tailored for projects managed within an Nx workspace.

What are @nrwl/jest's main functionalities?

Simplified Jest Configuration

Allows for simplified and centralized Jest configuration within an Nx workspace, making it easier to manage and share configurations across multiple library and application projects.

{
  "jestConfig": "./jest.config.js",
  "tsConfig": "./tsconfig.spec.json",
  "setupFile": "./src/test-setup.ts"
}

Parallel Test Execution

Enables parallel execution of tests across multiple projects within the workspace, significantly reducing the total time required for running tests in large projects.

nx run-many --target=test --all --parallel

Test Affected Projects

Identifies and runs tests only for the projects affected by recent changes, improving efficiency in continuous integration pipelines by skipping tests for unchanged projects.

nx affected:test

Other packages similar to @nrwl/jest

jest

Jest is the underlying testing framework that @nrwl/jest configures and enhances for use within Nx workspaces. While Jest can be used independently for testing JavaScript and TypeScript projects, @nrwl/jest provides additional integrations and optimizations for monorepo setups.

mocha

Mocha is another popular JavaScript test framework that can be used for unit and integration testing. Unlike @nrwl/jest, which is tailored for Jest and Nx workspaces, Mocha offers a more general-purpose testing solution without specific optimizations for monorepos or Nx.

karma

Karma is a test runner developed by the AngularJS team, designed to work with any framework. It differs from @nrwl/jest by focusing on executing tests in real browsers, providing a more integrated environment for testing browser-specific features. However, it lacks the monorepo-specific enhancements provided by @nrwl/jest.

README

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Nx: Smart, Fast and Extensible Build System

Nx is a next generation build system with first class monorepo support and powerful integrations.

This package is a Jest plugin for Nx.

Getting Started

Creating an Nx Workspace

Using npx

npx create-nx-workspace

Using npm init

npm init nx-workspace

Using yarn create

yarn create nx-workspace

The create-nx-workspace command will ask you to select a preset, which will configure some plugins and create your applications to help you get started.

? What to create in the new workspace (Use arrow keys)
❯ apps              [an empty workspace with no plugins with a layout that works best for building apps]
  core              [an empty workspace with no plugins set up to publish npm packages (similar to yarn workspaces)]
  ts                [an empty workspace with the JS/TS plugin preinstalled]
  react             [a workspace with a single React application]
  angular           [a workspace with a single Angular application]
  next.js           [a workspace with a single Next.js application]
  nest              [a workspace with a single Nest application]
  express           [a workspace with a single Express application]
  web components    [a workspace with a single app built using web components]
  react-native      [a workspace with a single React Native application]
  react-express     [a workspace with a full stack application (React + Express)]

Select the preset that works best for you

Adding Nx to an Existing Monorepo

Run:

npx add-nx-to-monorepo@latest

Documentation & Resources

A few links to help you get started:

• Nx.Dev: Documentation, Guides, Interactive Tutorials
• Tutorial: Adding Nx to an Existing Monorepo
• Official Nx YouTube Channel
• Blog Posts About Nx