# Write browser DOM tests with Bun and happy-dom (/docs/guides/test/happy-dom)

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Related: [Run your tests with the Bun test runner](/docs/guides/test/run-tests.md), [Run tests in watch mode with Bun](/docs/guides/test/watch-mode.md), [Migrate from Jest to Bun's test runner](/docs/guides/test/migrate-from-jest.md), [Mock functions in `bun test`](/docs/guides/test/mock-functions.md), [Spy on methods in `bun test`](/docs/guides/test/spy-on.md), [Set the system time in Bun's test runner](/docs/guides/test/mock-clock.md)

Use [Happy DOM](https://github.com/capricorn86/happy-dom) to write browser tests with Bun's test runner. Happy DOM implements mocked versions of browser APIs like `document` and `location`.

***

Install `@happy-dom/global-registrator`.

```sh terminal icon="terminal"
bun add -d @happy-dom/global-registrator
```

***

This module exports a "registrator" that injects the mocked browser APIs into the global scope.

```ts happydom.ts icon="/icons/typescript.svg"
import { GlobalRegistrator } from "@happy-dom/global-registrator";

GlobalRegistrator.register();
```

***

This file needs to run before any of your test files. That's a job for Bun's built-in [*preload*]() option. Create a `bunfig.toml` file in the root of your project (if it doesn't already exist) and add the following lines.

The `./happydom.ts` file should contain the registration code from the previous step.

```toml bunfig.toml icon="settings"
[test]
preload = "./happydom.ts"
```

***

Now `bun test` executes `happydom.ts` before your test files, so you can write tests that use browser APIs.

```ts dom.test.ts icon="/icons/typescript.svg"
import { test, expect } from "bun:test";

test("set button text", () => {
  document.body.innerHTML = `<button>My button</button>`;
  const button = document.querySelector("button");
  expect(button?.innerText).toEqual("My button");
});
```

***

With Happy DOM registered, the test passes.

```sh terminal icon="terminal"
bun test
```

```txt

dom.test.ts:
✓ set button text [0.82ms]

 1 pass
 0 fail
 1 expect() calls
Ran 1 test across 1 file. [125.00ms]
```

***

See the [Happy DOM repo](https://github.com/capricorn86/happy-dom) and [DOM testing](/test/dom).