Function renderSmoothText

apps/sim/hooks/use-smooth-text.test.tsx:20–46

* Minimal dependency-free hook harness (the repo has no `@testing-library/react`). Mounts the hook in * a real React root under jsdom so effects and refs run exactly as in the app. Fake timers keep the * paced reveal from advancing, so each assertion observes the synchronous reveal decision only.

(initial: ProbeProps)

 * paced reveal from advancing, so each assertion observes the synchronous reveal decision only.
 */
function renderSmoothText(initial: ProbeProps) {
  ;(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true
  const container = document.createElement('div')
  const root: Root = createRoot(container)
  const props = { ...initial }
  let latest = ''

  function Probe(p: ProbeProps) {
    latest = useSmoothText(p.content, p.isStreaming, { snapOnNonAppend: p.snapOnNonAppend })
    return null
  }

  const render = () =>
    act(() => {
      root.render(<Probe {...props} />)
    })
  render()

  return {
    value: () => latest,
    rerender: (next: Partial<ProbeProps>) => {
      Object.assign(props, next)
      render()
    },
    unmount: () => act(() => root.unmount()),
  }
}

const LONG = `# Existing Document\n\n${'Lorem ipsum dolor sit amet, '.repeat(8)}`