browser

Stand-ins for the browser surfaces a test environment cannot supply: windows that message each other across origins, and a ResizeObserver the test drives.

Usage

Unlike /dom, importing this entry changes nothing on the global, and none of it needs jsdom. Each stand-in is typed as the browser interface it replaces, so it goes straight into code that expects a Window without a cast.

Windows that message each other

createWindowPair returns two windows wired the way a page and the frame or popup it opened are. Posting to one delivers to that window's listeners with the other window as the event's source and the other window's origin as its origin:

import { expect, it, waitUntil } from '@hyperfrontend/testing'
import { createWindowPair } from '@hyperfrontend/testing/browser'
import { connect } from './connect'

it('connects a host and its frame', async () => {
  const [host, frame] = createWindowPair({ origins: ['https://host.test', 'https://frame.test'] })
  const hostSide = connect({ listenOn: host, peer: frame })
  const frameSide = connect({ listenOn: frame, peer: host })

  await waitUntil(() => hostSide.isOpen() && frameSide.isOpen())

  expect(frame.posted()).toEqual([expect.objectContaining({ type: 'HELLO' })])
})

createFakeWindow is a single window with no counterpart: it records what is posted to it, and receive dispatches a message to its listeners as if another origin had sent it.

ResizeObserver

installResizeObserver puts a ResizeObserver on the global and returns the controller that sends its notifications:

const observers = installResizeObserver()
const panel = mountPanel(container)

observers.resize(container, { width: 320, height: 200 })

expect(panel.layout()).toBe('compact')

Observers behave like real ones, observing, unobserving and disconnecting, and each entry carries the content rectangle and every box size. A callback runs only when the test calls resize, never on its own, not even for the initial notification a browser sends when observation starts. resizeLate also reaches observers that have stopped watching the element, the way a notification already queued when observation stopped still arrives, for testing code that must ignore one. The stub is installed as a stubbed global, so jest.restoreAllMocks removes it.