nock

What is nock?

The nock npm package is a powerful HTTP server mocking and expectations library for Node.js. It allows developers to test modules that perform HTTP requests in isolation. By intercepting outgoing HTTP requests and providing mock responses, nock enables a more controlled and predictable testing environment.

What are nock's main functionalities?

Intercepting HTTP Requests

This feature allows you to intercept an HTTP GET request to a specified URL and provide a custom response.

const nock = require('nock');
const http = require('http');

nock('http://example.com')
  .get('/resource')
  .reply(200, 'domain matched');

http.get('http://example.com/resource', (res) => {
  // This will receive the mocked response
});

Specifying Response Status and Body

With nock, you can specify the HTTP response status and body for a mocked endpoint, allowing you to simulate different server responses.

const nock = require('nock');

nock('http://example.com')
  .post('/login')
  .reply(401, { error: 'Unauthorized' });

Dynamic Response Functions

Nock can use functions to dynamically generate responses based on the incoming request data.

const nock = require('nock');

nock('http://example.com')
  .get('/data')
  .reply(200, (uri, requestBody) => {
    return { data: 'Dynamic response based on request' };
  });

Recording and Playback

Nock can record HTTP requests and responses and then play them back, which is useful for creating fixtures or reproducing issues.

const nock = require('nock');

nock.recorder.rec();
// Perform HTTP requests
// Nock will record the requests and responses
// Stop recording
nock.recorder.play();

Specifying Request Headers

This feature allows you to specify expected request headers and mock responses accordingly, which is useful for testing authentication and other header-dependent functionality.

const nock = require('nock');

nock('http://example.com', {
  reqheaders: {
    'authorization': 'Bearer token',
    'content-type': 'application/json'
  }
})
.get('/protected/resource')
.reply(200, 'Authenticated content');

Other packages similar to nock

sinon

Sinon is a testing utility that focuses on spies, stubs, and mocks. While it does not specialize in HTTP request mocking like nock, it can be used in conjunction with other libraries to achieve similar results.

axios-mock-adapter

This package is specifically designed to work with axios, a popular HTTP client. It allows for mocking axios requests, similar to how nock mocks Node.js HTTP requests, but is limited to axios instances.

fetch-mock

Fetch-mock is designed to mock HTTP requests made using the fetch API. It offers similar functionality to nock but is tailored for the global fetch method rather than Node.js HTTP modules.

jest-mock-axios

Jest-mock-axios is a mock for axios library that is specifically built to work with Jest testing framework. It provides a simple and easy-to-use API for mocking axios requests and responses.

supertest

Supertest is a library that allows you to test HTTP servers by making requests to them. It is often used in conjunction with a real server instance, unlike nock which mocks the HTTP requests at a lower level.

README

Nock

HTTP Server mocking for Node.js

Nock can be used to test modules that perform HTTP requests in isolation.

For instance, if a module performs HTTP requests to a CouchDB server or makes HTTP requests to the Amazon API, you can test that module in isolation.

Install

$ npm install nock

Use

On your test, you can do this:

var nock = require('nock');

couchdb = mokk('http://myapp.iriscouch.com')
            .get('/users/1')
            .reply