Jest click event not firing a ref

Question

I created an iframe component with ref and I wanted to create a unit test for that component, then I created a mock iframe so that the component could be run in the unit test, unfortunately the unit test failed, what's wrong with the following code, I'm a beginner at Jest. So how do you make the unit test successful?

component

import { forwardRef, useRef, useImperativeHandle } from 'react';
const Iframe = forwardRef(function Iframe(props, ref) {
  const iframeRef = useRef(null);
  useImperativeHandle(ref, () => {
    return {
      postMessage() {
        iframeRef.current.contentWindow.postMessage(JSON.stringify({data: 'hello !'}), '*')
      },
    };
  }, []);
  return <iframe {...props} ref={iframeRef} />;
});

export default Iframe;

mock

// __mock__/iframe.js
import { useRef } from 'react';
import Iframe from './Iframe';
export default function App() {
  const ref = useRef(null);
  function handleClick() {
    ref.current.postMessage({data: 'hello !'});
  }
  return (
    <div>
      <Iframe src={'https://www.google.com/'} ref={ref} />
      <button onClick={handleClick}>
        Send Message
      </button>
    </div>
  );
}

jest

import * as React from 'react'
import { render, fireEvent, screen } from '@testing-library/react'
import Iframe from '../__mock__/iframe'
describe('iframe', () => {
  it('call postMessage', () => {
    render(<Iframe />)
    const handleClick = jest.fn()
    const button = screen.getByText(/Send Message/i)
    fireEvent.click(button)
    expect(handleClick).toHaveBeenCalled()
  })
})

test failed