---
title: Wrangler's unstable_startWorker()
description: Write integration tests using Wrangler's `unstable_startWorker()` API
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Wrangler's unstable\_startWorker()

Note

For most users, Cloudflare recommends using the Workers Vitest integration. If you have been using `unstable_dev()`, refer to the [Migrate from unstable\_dev() guide](https://developers.cloudflare.com/workers/testing/vitest-integration/migration-guides/migrate-from-unstable-dev/).

Warning

`unstable_startWorker()` is an experimental API subject to breaking changes.

If you do not want to use Vitest, consider using [Wrangler's unstable\_startWorker() API](https://developers.cloudflare.com/workers/wrangler/api/#unstable%5Fstartworker). This API exposes the internals of Wrangler's dev server, and allows you to customise how it runs. Compared to using [Miniflare directly for testing](https://developers.cloudflare.com/workers/testing/miniflare/writing-tests/), you can pass in a Wrangler configuration file, and it will automatically load the configuration for you.

This example uses `node:test`, but should apply to any testing framework:

TypeScript

```
import assert from "node:assert";import test, { after, before, describe } from "node:test";import { unstable_startWorker } from "wrangler";
describe("worker", () => {  let worker;
  before(async () => {    worker = await unstable_startWorker({ config: "wrangler.json" });  });
  test("hello world", async () => {    assert.strictEqual(      await (await worker.fetch("http://example.com")).text(),      "Hello world",    );  });
  after(async () => {    await worker.dispose();  });});
```

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