Testing & Mocking Packages
Testing frameworks, assertion libraries, and mocking tools for writing reliable unit, integration, and end-to-end tests (testify, pytest, Vitest).
Packages in Testing & Mocking
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Playwright
Cross-browser end-to-end web testing and browser automation with a single API for Chromium, Firefox, and WebKit.
jsdom
A pure-JavaScript implementation of the WHATWG DOM and HTML standards for Node.js.
React Testing Library
Simple and complete React DOM testing utilities that encourage good testing practices.
jest-dom
Custom Jest matchers for asserting on the state of the DOM in your tests.
user-event
Simulates the full sequence of real browser events so Testing Library tests behave the way an actual user does.
Storybook
The industry-standard workshop for building, documenting, and testing UI components in isolation, across every major frontend framework.
DOM Testing Library
Simple, framework-agnostic DOM query utilities that test your UI the way real users interact with it.
Faker
Generate massive amounts of realistic fake data for testing, seeding, and mocking in JavaScript and TypeScript.
MSW (Mock Service Worker)
Seamless REST and GraphQL API mocking for browser and Node.js
mocha
The classic, battle-tested JavaScript test framework for Node.js and the browser, built around flexible async testing and pluggable reporters.
Chai
BDD/TDD assertion library for Node.js and the browser, framework-agnostic
identity-obj-proxy
An ES6 Proxy that echoes back every key you access, built to mock CSS Modules and other webpack style imports in Jest tests.
pytest-mock
A pytest plugin that provides a `mocker` fixture wrapping Python's `unittest.mock`, with automatic teardown between tests.
go-sqlmock
A mock sql/driver implementation for Go that simulates database behavior in tests without a real database connection.
jest-junit
A Jest reporter that converts test results into JUnit-compatible XML for CI dashboards and test-analytics tools.
deep-equal
A standalone port of Node's own assert.deepEqual algorithm, giving spec-accurate deep equality checks in Node and the browser alike.
vitest-canvas-mock
A drop-in HTML canvas mock for Vitest that emulates spec-accurate CanvasRenderingContext2D behavior in jsdom test environments.
mockall
A powerful mock object library for Rust unit testing.
gock
Versatile HTTP traffic mocking for Go, intercepting any net/http-based client for deterministic tests.
chrome-remote-interface
A Node.js client for the Chrome DevTools Protocol, exposing every browser command, event, and type as a plain JavaScript API.
@sinonjs/fake-timers
Deterministic fake implementations of setTimeout, setInterval, Date, and other timer APIs for fast, reliable JavaScript tests.
memlab
Meta's end-to-end framework for finding JavaScript memory leaks and analyzing heap snapshots
user-agents
A JavaScript library that generates realistic, frequency-weighted random user agents and browser fingerprints from a dataset refreshed daily.
time-machine
Travel through time in your Python tests by mocking datetime and time at the C level.
