How do I use Nock with Axios in my Node.js tests?

Set axios.defaults.adapter to 'http' and possibly configure Jest's moduleNameMapper for axios. The README's 'Axios' section provides a full example to ensure requests are intercepted.

Nock vs Mock Service Worker: which is better for testing?

Nock is ideal for Node.js backend tests with low-level HTTP mocking. Mock Service Worker runs in browsers and supports REST/GraphQL, making it better for frontend or cross-environment testing.

How to record HTTP requests with Nock for fixture generation?

Use nock.recorder.rec() with options like output_objects to capture real interactions. The 'Recording' section explains how to save and replay these as test fixtures.

Why isn't Nock intercepting my requests in an ES module?

ES modules imported before Nock aren't intercepted. Fix this by running Node with --import=nock or setting NODE_OPTIONS, as mentioned in the 'Common issues' section.

How to handle retries when mocking error responses with Nock?

Libraries like Got auto-retry failed requests. Disable retries with { retry: 0 } in Got or use a custom client, as described in the 'Common issues' for error responses.

What are common pitfalls when using Nock with Jest?

Memory leaks can occur if nock.restore() isn't called after tests. Also, ensure Nock is activated and scopes are cleaned to avoid interference between test suites.

Open-Awesome

Nock

MITJavaScriptv14.0.13

A comprehensive HTTP server mocking and expectations library for Node.js to test modules in isolation.

GitHub

13.1k stars754 forks0 contributors

What is Nock?

Nock is an HTTP server mocking and expectations library for Node.js that intercepts and simulates HTTP requests. It allows developers to test modules that rely on external APIs or services in isolation by mocking their responses without making actual network calls. This ensures tests are fast, reliable, and independent of external dependencies.

Target Audience

Node.js developers writing unit or integration tests for applications that make HTTP requests, such as API clients, microservices, or modules interacting with third-party services like CouchDB or Amazon APIs.

Value Proposition

Developers choose Nock for its comprehensive feature set, including precise request matching, flexible response simulation, and recording capabilities. It integrates seamlessly with Node's HTTP stack, provides detailed expectation tracking, and is widely adopted in the Node.js ecosystem for reliable test isolation.

Overview

HTTP server mocking and expectations library for Node.js

Use Cases

Best For

Testing API clients without hitting real endpoints
Simulating error responses (e.g., 4xx/5xx status codes) from external services
Isolating unit tests for modules that depend on HTTP requests
Recording and replaying HTTP interactions for consistent test fixtures
Mocking third-party services like GitHub, Dropbox, or AWS APIs
Testing race conditions and timeouts with delayed responses

Not Ideal For

Projects needing to mock WebSocket or non-HTTP protocols (Nock is HTTP/HTTPS only)
Teams using Jest without proper cleanup routines, due to memory leak risks
Browser-based testing environments (Nock is Node.js-specific)
Applications where you prefer high-level API mocking over low-level HTTP interception

Pros & Cons

Pros

Precise Request Matching

Nock intercepts requests based on hostname, path, method, query strings, headers, and body using strings, regex, or functions, as detailed in the 'Specifying hostname' and 'Specifying path' sections.

Flexible Response Simulation

It can reply with static data, JSON, files, streams, or dynamic callbacks, including custom status codes and headers, enabling realistic mock setups without network calls.

Expectation Tracking

Methods like .isDone() and .pendingMocks() help ensure all mocked requests are made, preventing false positives in tests, as explained in the 'Expectations' section.

Recording and Playback

The Nock Back feature records real HTTP interactions to generate fixtures for playback, simplifying test maintenance and setup, covered in the 'Recording' and 'Nock Back' sections.

Cons

ES Module Interception Issues

The README admits requests from ES modules aren't intercepted unless Node is preloaded with Nock via --import flag, adding complexity for modern codebases.

Memory Leaks with Jest

Nock can cause memory issues in Jest tests if nock.restore() isn't called after each suite, requiring manual cleanup that's easy to overlook.

Configuration Overhead for Libraries

Using Nock with Axios requires setting axios.defaults.adapter and adjusting Jest configs, as noted in the 'Axios' section, adding setup friction.

Frequently Asked Questions

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