Head-to-Head: Polly.JS vs MSW Analysis


v6.0.6(3 months ago)

This package is actively maintained.Types definitions are bundled with the npm packageNumber of direct dependencies: 9Monthly npm downloads

@pollyjs/core is a JavaScript testing library that helps developers record, replay, and stub HTTP interactions. It can be integrated with any testing framework and provides a powerful API for testing network requests. With Polly.js, you can simulate scenarios like slow networks and server errors to ensure your application handles them gracefully. It also supports parallel testing and can be used in different environments, including browser testing and command-line tools. Its comprehensive documentation and plugin system make it easy to customize and extend its functionality.

Alternatives: nock, miragejs, msw

Tags: javascripttestinghttpnetwork-requestsmocking


v1.3.2(4 days ago)

This package is actively maintained.Types definitions are bundled with the npm packageNumber of direct dependencies: 19Monthly npm downloads

MSW is a comprehensive mocking solution and network request interception library for modern web applications. It allows developers to create realistic mock backends by intercepting network requests at the network layer, and providing custom responses based on the request data. MSW is also a powerful tool for testing and debugging frontend applications, as it lets you simulate various network conditions and responses in a controlled environment.

Alternatives: nock, sinon, mock-javascript

Tags: javascriptmockingrequest-interceptiontestingdebuggingweb-development



Both @pollyjs/core and msw are popular npm packages within the JavaScript community. Although @pollyjs/core has been around for longer, msw has gained significant attention and popularity in recent years.

Mocking and Stubbing

@pollyjs/core is primarily focused on advanced network request handling and offers powerful features for recording, replaying, and persisting HTTP interactions. It integrates seamlessly with different testing frameworks and allows you to stub responses and test network-dependent code effectively. On the other hand, msw is a modern and efficient mock service worker library that allows you to intercept and mock network requests made by the client application. It provides an intuitive API for handling requests, and its integration with testing frameworks is also straightforward.

Testing Ecosystem Integration

Both packages have excellent integrations with popular testing frameworks such as Jest, Mocha, and Cypress. @pollyjs/core, being more established, has a wide range of plugins and extensions that enhance its compatibility with multiple testing frameworks. Similarly, msw also has solid integration support and is frequently used in combination with testing frameworks for frontend and API testing.

Developer Experience

In terms of developer experience, both packages provide a smooth and intuitive API. However, @pollyjs/core is more feature-rich and offers additional capabilities such as request and response filtering, middleware support, and event hooks. msw, on the other hand, focuses on simplicity and ease of use, providing a clear and concise API for handling network requests.

Supported Environments

@pollyjs/core is primarily aimed at testing client-side JavaScript and supports various environments, including browser-based testing frameworks like Cypress and testing in Node.js environments. msw is built specifically for mocking network requests in client-side applications using modern JavaScript frameworks like React, Angular, and Vue.js.

Documentation and Community Support

Both packages have well-documented APIs and provide comprehensive guides that help users get started quickly. @pollyjs/core has been around for longer, so it has a stronger community presence with more active contributors. msw, although relatively newer, has a growing community and responsive maintainers.