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vitest-fetch-mock

library0.4.5jsnpmunverified

Vitest Fetch Mock (v0.4.5) is a fetch mocking library for Vitest, forked from jest-fetch-mock. It mocks the global fetch API using Vitest's vi.fn() under the hood, providing a simple API to mock responses, inspect calls, and reset state. Works with Vitest >=2.0.0 and Node >=18. Unlike nock or msw, it directly replaces global.fetch without interceptors or service workers. Ships TypeScript types.

testing

npm install vitest-fetch-mock

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · VITEST-FETCH-MOCK

vitest-fetch-mock

testingjavascriptv0.4.5

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.

createFetchMock

✓ import createFetchMock from 'vitest-fetch-mock';

Default export function. Must pass vi instance from vitest.

fetchMock

✓ fetchMock.mockResponse(JSON.stringify({ok: true}));

✗ vi.mock('fetch'); fetch.mockResponse(...)

fetchMock is a global set after calling enableMocks().

globalThis.fetch

✓ globalThis.fetch = fetchMock;

✗ global.fetch = fetchMock;

Uses globalThis for modern environments; avoid global.

Shows setup of createFetchMock with vi, enabling mocks, and a simple test with mockResponse and assertions.

import createFetchMock from 'vitest-fetch-mock'; import { vi, describe, it, expect } from 'vitest'; const fetchMocker = createFetchMock(vi); fetchMocker.enableMocks(); describe('fetch tests', () => { it('should mock fetch', async () => { fetchMock.mockResponse(JSON.stringify({ data: 'test' })); const response = await fetch('/api'); const body = await response.json(); expect(body.data).toBe('test'); expect(fetchMock).toHaveBeenCalledTimes(1); }); });

Debug

Known issues

breakingIn v0.4.0, fetch mock switched from polyfill to global fetch, requires Node >=18. Older Node versions break.

fix

Use v0.2.2 for Node <18 or Vitest 1.x.

affects: >=0.4.0

breakingenableMocks() no longer accepts arguments; previously (v0.2.2) could pass a custom fetch implementation.

fix

Remove any arguments from enableMocks() call.

affects: >=0.4.0

gotchafetchMock.mockReject() does not return a valid Response object; calls to .json() or .text() will fail.

fix

Use mockRejectOnce with a new Error(), or mockResponse with status 500.

affects: >=0.1.0

deprecatedmockOnce() is deprecated; use mockResponseOnce() instead.

fix

Replace mockOnce() with mockResponseOnce().

affects: >=0.4.0

gotchaIf you forget to call enableMocks(), global fetch remains unmocked and tests may hit real network.

fix

Call fetchMocker.enableMocks() in setup file or beforeAll.

affects: >=0.1.0

Errors

Common errors & fixes

TypeError: fetchMock.mockResponse is not a function

fetchMock global not initialized because enableMocks() not called or imported incorrectly.

fix

Call fetchMocker.enableMocks() after createFetchMock(vi).

ReferenceError: vi is not defined

Using vitest-fetch-mock without Vitest running (e.g., in plain Node test).

fix

Ensure test files are run by Vitest, e.g., npx vitest run.

Error: fetch is not a function

Node version <18 lacks global fetch; vitest-fetch-mock v0.4+ requires Node >=18.

fix

Upgrade to Node >=18 or install vitest-fetch-mock@0.2.2.

Vitest 2.x peer dependency not met

Installed with Vitest 1.x which is incompatible with v0.4+.

fix

Use vitest-fetch-mock@0.2.2 for Vitest 1.x, or upgrade Vitest to >=2.

Upgrade

Version history

0.4.5latest on npm

Audit

Dependencies

vitestrequiredPeer dependency; required to utilize vi.fn() and mock API

Agent activity

8 hits · last 30 days

node

Resources

githubhttps://github.com/IanVS/vitest-fetch-mock ↗

packagevitest-fetch-mock ↗

homepagehttps://github.com/IanVS/vitest-fetch-mock#readme ↗