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Nock

Open Source

HTTP server mocking and expectations library for Node.js — intercept outgoing requests in tests.

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Pricing

Free / Open source

Type

Automation

Languages

JavaScript, TypeScript

// VERDICT

Reach for Nock when you want to intercept and mock outgoing HTTP from Node tests deterministically. Skip it when you're not in Node, want browser-level mocking (MSW), or need to test against the real service.

Best for

HTTP server mocking for Node - intercepting outgoing HTTP requests and returning canned responses, so tests run without hitting real external services.

Avoid when

You're not in Node, you want to mock at the browser/network level (MSW), or you need real integration against the service.

CI/CD fit

Library in Node tests · intercepts HTTP · deterministic CI

Languages

JavaScript · TypeScript

Team fit

Node/JS teams · Testing code that calls HTTP APIs · Deterministic unit tests

Setup

Easy

Maintenance

Low

Learning

Intermediate

Licence

Free / Open source

// BEST FOR

  • Intercepting outgoing HTTP requests in Node
  • Returning canned responses for external APIs
  • Making tests deterministic without real services
  • Asserting requests were made as expected
  • Simulating errors/timeouts from dependencies
  • Fast, isolated unit tests of API-calling code

// AVOID WHEN

  • You're not in Node
  • Browser/network-level mocking is needed (MSW)
  • You need real integration against the service
  • You want a standalone mock server (WireMock/Mockoon)
  • End-to-end realism is required
  • Minimal mocking suffices

// QUICK START

npm install -D nock
// nock('https://api.example.com').get('/users/1').reply(200, {id:1});

// ALTERNATIVES TO CONSIDER

ToolChoose it when
Sinon.jsYou want general spies/stubs/mocks, not just HTTP.
MSWYou want network-level mocking for frontend/browser tests.
WireMockYou want a standalone mock HTTP server.

// FEATURES

  • Intercept HTTP requests at the Node.js http module level
  • Match by method, URL, headers, and request body
  • Replay recorded fixtures with nock.recorder
  • Strict allow-no-unmocked mode to catch unintended calls
  • Per-test isolation via nock.cleanAll and nock.restore

// PROS

  • Zero network in tests — fast and deterministic
  • Mature, widely used in the Node.js ecosystem
  • Recording mode makes fixture creation easy
  • Composes naturally with Mocha, Jest, Vitest, and Tap

// CONS

  • Node.js-only — does not intercept browser requests
  • Doesn't intercept fetch by default in older Node versions
  • Mismatched interceptors can produce confusing test failures

// EXAMPLE QA WORKFLOW

  1. Install Nock

  2. Declare intercepts in test setup

  3. Return canned responses (incl. errors)

  4. Assert requests were made as expected

  5. Clean up intercepts between tests

  6. Keep mocks aligned with the real contract

// RELATED QA.CODES RESOURCES

Glossary