plugin MSW isn't working with vitest

[HelenaVeltri]

I'm trying to config MSW into my project, i created the base files with the handlers, and modified the "vitest.config.ts" and the setup file for it, adding the server

(import { setupServer } from "msw/node";
import { handlers } from "./handlers";
export const server = setupServer(...handlers);
)

into the setupTest config:

import { createVuetify } from "vuetify";
import * as components from "vuetify/components";
import * as directives from "vuetify/directives";
import { beforeAll, afterEach, afterAll } from "vitest";
import { server } from "../../tests/mockups/MockServiceWorker/testMSW";

const vuetify = createVuetify({
  components,
  directives,
});

config.global.plugins = [vuetify];

//Configura o MSW
beforeAll(() => server.listen({ onUnhandledRequest: "error" }));
afterEach(() => server.resetHandlers());
afterAll(() => server.close());
) 

but, when i run my test with the server import return this error:

ReferenceError: TransformStream is not defined
 ❯ node_modules/@mswjs/interceptors/src/interceptors/fetch/utils/followRedirect.ts:104:12
 ❯ node_modules/@mswjs/interceptors/lib/node/interceptors/fetch/index.mjs:1:31
      1| import {
      2|   FetchInterceptor
       |            ^
      3| } from "../../chunk-WI4WZWP4.mjs";
      4| import "../../chunk-TX5GBTFY.mjs";

 Test Files  1 failed (1)
      Tests  no tests
   Start at  14:59:40
   Duration  1.16s (transform 164ms, setup 0ms, collect 0ms, tests 0ms, environment 305ms, prepare 416ms)

 FAIL  Tests failed. Watching for file changes...
       press h to show help, press q to quit

i tried running in the jsdom and node enviroment and still doesn't working :(

Someone have/had this same problem before?

[stijnvanhulle]

@HelenaVeltri This has something to do with your Node version.

MSW v2+ relies on the Web Fetch API, which internally uses TransformStream when mocking or following redirects.

Vitest runs by default in a Node-like environment, and:
• Node 18+ → ✅ includes TransformStream natively
• Node 16 or lower → ❌ missing TransformStream, causing

You can add the following prefill to vitest.setup.ts

import { TransformStream } from 'web-streams-polyfill/ponyfill';

// Polyfill TransformStream if not present
if (!globalThis.TransformStream) {
  // @ts-expect-error
  globalThis.TransformStream = TransformStream
}