expect-fetch

Jest DOM-style assertions for native Fetch API requests and responses.

expect-fetch adds expressive HTTP matchers to Vitest without mocking globalThis.fetch. Use it to test Next.js route handlers, Remix loaders, SvelteKit and Astro endpoints, Hono applications, Cloudflare Workers, or any code that produces native Request or Response objects.

import 'expect-fetch/vitest';

const response = await app.request('/users/123');

expect(response).toHaveStatus(200);
expect(response).toHaveHeader('content-type', /json/);

await expect(response).toHaveJson({
  id: '123',
  name: 'Ada',
});

Request assertions use the same API:

expect(request).toHaveMethod('POST');
expect(request).toHaveUrl('/users?page=2');
expect(request).toHaveQuery({ page: '2' });
expect(request).toHaveHeader('authorization', /^Bearer /);

await expect(request).toHaveJson({ name: 'Ada' });

Installation

npm install --save-dev expect-fetch

Add the integration to a Vitest setup file:

// test/setup.ts
import 'expect-fetch/vitest';

// vitest.config.ts
import { defineConfig } from 'vitest/config';

export default defineConfig({
  test: {
    setupFiles: ['./test/setup.ts'],
  },
});

You can also import the integration directly in an individual test file.

Matchers

toHaveStatus

expect(response).toHaveStatus(201);

toHaveHeader

Header names are case-insensitive. Values can be exact strings or regular expressions. Requests and responses are supported.

expect(response).toHaveHeader('content-type');
expect(response).toHaveHeader('content-type', /application\/json/);
expect(response).toHaveHeader('x-request-id', 'req_123');

toHaveJson

The request or response is cloned before its body is read, so the matcher does not consume the original body. Vitest asymmetric matchers are supported.

await expect(response).toHaveJson({
  id: expect.any(String),
  role: 'admin',
});

toHaveText

await expect(response).toHaveText('Not found');
await expect(response).toHaveText(/not found/i);

toHaveFormData

Repeated fields are represented as arrays. Requests and responses are supported.

await expect(request).toHaveFormData({
  name: 'Ada',
  roles: ['admin', 'author'],
  avatar: expect.any(File),
});

toHaveMethod

Method comparison is case-insensitive.

expect(request).toHaveMethod('POST');

toHaveUrl

Absolute URLs, URL objects, regular expressions, and relative URLs containing the path, query, and fragment are supported.

expect(request).toHaveUrl('/users?page=2');
expect(request).toHaveUrl(/^https:\/\/example\.com\/users/);

toHaveQuery

Query values are decoded. Repeated parameters are represented as arrays.

expect(request).toHaveQuery({
  q: 'Ada Lovelace',
  tag: ['math', 'code'],
});

toRedirectTo

Without an explicit status, any status from 300 through 399 is accepted.

expect(response).toRedirectTo('/login');
expect(response).toRedirectTo('/login', 307);

toSetCookie

expect(response).toSetCookie('session', {
  value: /^eyJ/,
  path: '/',
  httpOnly: true,
  secure: true,
  sameSite: 'lax',
  maxAge: 3600,
});

Supported expectations are value, domain, path, expires, maxAge, secure, httpOnly, and sameSite. Omitted fields are not checked.

Set-Cookie is intentionally supported for server-side response tests. Browsers do not expose this response header to client-side JavaScript.

Why not fetch-mock?

Fetch mocking tools fake the server that your code calls. expect-fetch verifies the Response produced by the server or handler you are building. They solve different problems and can be used together.

Compatibility

• Node.js 20 or newer
• Vitest 2, 3, or 4
• Any framework using standards-compatible Fetch API objects

The matchers use structural checks rather than instanceof Response, allowing responses created in another JavaScript realm or by compatible runtimes. Failure diagnostics redact Authorization, Proxy-Authorization, Cookie, and Set-Cookie values so credentials do not leak into test or CI logs.

License

MIT

Contributing and security

See CONTRIBUTING.md for development and release guidance. Please use the private process in SECURITY.md to report vulnerabilities.