Nock HTTP Mocking for Node.js

Nock is a robust HTTP server mocking and expectations library designed specifically for Node.js environments. It enables developers to test modules that make outbound HTTP/HTTPS requests in isolation by intercepting network traffic and responding with predefined data. The current stable release series is v14, with v14.0.12 being the latest as of April 2026. An actively developed v15 beta series introduces new features such as `passthrough()` for granular control over unmocked requests and improved error handling, but is not yet recommended for production use due to an accidental v15.0.0 release that was later deprecated. Nock maintains an active release cadence, frequently publishing bug fixes and beta updates. Its key differentiators include comprehensive control over request matching (by host, path, query, body, headers, and HTTP verb), the ability to define repeatable or one-time responses, and functionalities for recording and playing back HTTP interactions using 'nock-back' for fixture-based testing. It aims to provide deep control over the network layer to facilitate reliable unit and integration testing without relying on actual network connectivity.