Nock vs Sinon.js: licensing, GitHub activity, and what each is actually for. Neutral comparison, no paid rankings.
Nock: Open source. 13,127 GitHub stars. HTTP server mocking and expectations library for Node.js. Record and replay HTTP interactions.
Sinon.js: Open source. 9,754 GitHub stars. Standalone test spies, stubs, and mocks for JavaScript. Works with any unit testing framework.