fix: add BroadcastChannel (#19)

Author: kettanaito

README.md

@@ -1,6 +1,11 @@
 <h1 align="center">jest-fixed-jsdom</h1>
 <p align="center">A superset of the JSDOM environment for Jest that respects Node.js globals.</p>
 
+<!-- prettier-ignore-start -->
+> [!WARNING]
+> **This package is never meant as a solution to anything**. This is a workaround. Please consider testing browser code in the actual browser. You can do so both in [Vitest](https://vitest.dev/guide/browser/) and in [Playwright](https://playwright.dev/docs/test-components) at the moment.
+<!-- prettier-ignore-end -->
+
 ## Motivation
 
 When you use Jest with JSDOM you are getting a broken test environment. Some Node.js globals cease to exist (e.g. `Request`, `Response`, `TextEncoder`, `TextDecoder`, `ReadableStream`<sup><a href="https://github.com/mswjs/msw/issues/1916">1</a></sup>), while others stop behaving correctly (e.g. `Event`, `MessageEvent`<sup><a href="https://github.com/nodejs/undici/issues/2663">2</a></sup>, `structuredClone()`<sup><a href="https://github.com/mswjs/msw/issues/1931">3</a></sup>). That is caused by `jest-environment-jsdom` and JSDOM relying on polyfills to implement standard APIs that have been available globally both in the browser and in Node.js for years.
@@ -37,6 +42,7 @@ This project "fixes" the following global APIs, overriding whichever polyfills t
 - `structuredClone()`
 - `URL`
 - `URLSearchParams`
+- `BroadcastChannel`
 
 ## Getting started
 

index.js

@@ -19,6 +19,8 @@ class FixedJSDOMEnvironment extends JSDOMEnvironment {
     this.global.structuredClone = structuredClone
     this.global.URL = URL
     this.global.URLSearchParams = URLSearchParams
+
+    this.global.BroadcastChannel = BroadcastChannel
   }
 }
 

index.test.js

@@ -1,4 +1,7 @@
 const { URL: BuiltinURL } = require('node:url')
+const {
+  BroadcastChannel: BuiltinBroadcastChannel,
+} = require('node:worker_threads')
 
 test('exposes "Blob"', async () => {
   expect(globalThis).toHaveProperty('Blob')
@@ -38,7 +41,9 @@ test('exposes "TextEncoderStream"', async () => {
     if (done) break
     chunks.push(...value)
   }
-  expect(Buffer.from(chunks)).toEqual(Buffer.from(new Uint8Array([104, 101, 108, 108, 111])))
+  expect(Buffer.from(chunks)).toEqual(
+    Buffer.from(new Uint8Array([104, 101, 108, 108, 111])),
+  )
 })
 
 test('exposes "TextDecoderStream"', async () => {
@@ -139,6 +144,22 @@ test('exposes "URLSearchParams" and makes it mockable', () => {
     .mockImplementation((key) => key === 'mocked_flag')
 
   expect(globalThis).toHaveProperty('URLSearchParams')
-  expect(new URL('http://localhost?other_non_mocked_flag').searchParams.has('other_non_mocked_flag')).toBe(false)
-  expect(new URL('http://localhost?other_non_mocked_flag').searchParams.has('mocked_flag')).toBe(true)
+  expect(
+    new URL('http://localhost?other_non_mocked_flag').searchParams.has(
+      'other_non_mocked_flag',
+    ),
+  ).toBe(false)
+  expect(
+    new URL('http://localhost?other_non_mocked_flag').searchParams.has(
+      'mocked_flag',
+    ),
+  ).toBe(true)
+})
+
+test('exposes "BroadcastChannel"', () => {
+  expect(globalThis).toHaveProperty('BroadcastChannel')
+
+  const channel = new BroadcastChannel('foo')
+  expect(channel).toBeInstanceOf(BuiltinBroadcastChannel)
+  channel.unref()
 })