vitest/web-worker and using fake timers

[danwoods89]

Hi there, I have a web worker which uses setTimeout inside. In my unit tests for it, vi.useFakeTimers and vi.advanceTimersByTime does not impact the setTimeout within the web worker. It never hits setTimeout's callback. If I use vi.getTimerCount it shows as 0.

Are fake timers supposed to work with web workers and I am simply doing something wrong? Many thanks.

import "@vitest/web-worker";

describe("GameClockWebWorker", () => {
  beforeEach(() => {
    vi.useFakeTimers();
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  it("should intialise a 10 minute timer", () => {
    // arrange
    const gameClockWebWorker = new Worker(new URL("./gameClockWebWorker.ts", import.meta.url), { type: "module" });

    // act
    gameClockWebWorker.postMessage(600000);
    
    vi.advanceTimersByTime(100);

    // assert
    gameClockWebWorker.onmessage = (e) => {
      expect(e.data).toEqual(600000);
    };

    gameClockWebWorker.terminate();
  });