msw-fetch-mock

library0.6.1jsnpmunverified

An undici-style fetch mock API built on top of MSW (Mock Service Worker) for testing. Version 0.6.1 supports Node.js (>=18), browser, and native (no MSW dependency) environments via subpath exports. It provides a familiar fluent API similar to Cloudflare Workers' fetchMock or Node.js undici's MockAgent. Key differentiators: integrates seamlessly with MSW, supports both MSW v1 (via /legacy) and v2, and allows sharing existing MSW servers. Peer dependency on MSW ^1.0.0 or ^2.12.7. Active development with CI, weekly downloads ~500.

testing

npm install msw-fetch-mock

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · MSW-FETCH-MOCK

msw-fetch-mock

testingjavascriptv0.6.1

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

fetchMock

✓ import { fetchMock } from 'msw-fetch-mock'

✗ import fetchMock from 'msw-fetch-mock'

Default export does not exist; use named import.

createFetchMock

✓ import { createFetchMock } from 'msw-fetch-mock'

✗ const { createFetchMock } = require('msw-fetch-mock')

Library is ESM-only; require() will not work.

fetchMock (native)

✓ import { fetchMock } from 'msw-fetch-mock/native'

✗ import { fetchMock } from 'msw-fetch-mock'

Use /native subpath to avoid MSW dependency.

Shows basic setup and usage of fetchMock for mocking an HTTP GET request in a test suite, including activation, cleanup, and assertion.

import { fetchMock } from 'msw-fetch-mock'; beforeAll(() => fetchMock.activate({ onUnhandledRequest: 'error' })); afterAll(() => fetchMock.deactivate()); afterEach(() => { fetchMock.assertNoPendingInterceptors(); fetchMock.reset(); }); it('mocks GET request', async () => { fetchMock .get('https://api.example.com') .intercept({ path: '/users', method: 'GET' }) .reply(200, { users: [{ id: '1', name: 'Alice' }] }); const res = await fetch('https://api.example.com/users'); const data = await res.json(); expect(data.users).toHaveLength(1); });

Debug

Known issues

gotchaOnly one MSW server can be active at a time. Using standalone activate() while another server is listening will throw an error.

fix

Use createFetchMock(server) to share an existing MSW server.

affects: >=0.0.0

deprecatedMSW v1 is supported via /legacy subpath but is considered legacy; MSW v1 is no longer actively maintained.

fix

Upgrade to MSW v2 and use the main entry or /node subpath.

affects: >=0.0.0

gotchaUnhandled requests in 'error' mode cause fetch() to reject, including requests to consumed one-time interceptors.

fix

Set onUnhandledRequest to 'warn' or 'bypass' if needed.

affects: >=0.0.0

breakingRequires Node.js >= 18. Older versions are not supported.

fix

Update Node.js to 18+.

affects: >=0.6.0

deprecatedThe standalone import 'msw-fetch-mock' may be deprecated in future in favor of explicit subpaths.

fix

Use explicit subpaths like 'msw-fetch-mock/node' for clarity.

affects: >=0.6.0

Errors

Common errors & fixes

Error: [MSW] Failed to activate: Another server is already listening.

Activating fetchMock standalone while an MSW server is already active.

fix

Use createFetchMock(server) to share the existing server.

ERR_REQUIRE_ESM: require() of ES Module not supported.

Using CommonJS require() to import the ESM-only package.

fix

Use import syntax or set type: 'module' in package.json.

TypeError: fetchMock.activate is not a function

Incorrect import; likely using default import instead of named import.

fix

Use import { fetchMock } from 'msw-fetch-mock'.

Error: fetchMock is not defined

Using /native subpath but MSW is not installed, or incorrect import path.

fix

Install msw or use import { fetchMock } from 'msw-fetch-mock/native'.

Upgrade

Version history

0.6.1latest on npm

Audit

Dependencies

mswoptionalpeer dependency; used for request interception in Node.js and browser environments

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/recca0120/msw-fetch-mock ↗

packagemsw-fetch-mock ↗

homepagehttps://github.com/recca0120/msw-fetch-mock#readme ↗