chromium/third_party/blink/web_tests/wpt_internal/forms/file/file-input-click.html

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<title>INPUT TYPE=FILE and click events</title>
<input type="file">
<script type="module">
import {mockFileChooserFactory} from '../resources/mock-file-chooser.js';

promise_test(async _ => {
  const file = document.querySelector('input');
  const x = file.offsetLeft + file.offsetWidth / 2;
  const y = file.offsetTop + file.offsetHeight / 2;

  const promise = new Promise(
      resolve => mockFileChooserFactory.addEventListener('open', resolve));

  eventSender.mouseMoveTo(x, y);
  eventSender.mouseDown();
  eventSender.mouseMoveTo(x, y);
  eventSender.mouseUp();

  const openEvent = await promise;
  assert_equals(openEvent.detail, 'kOpen');
}, 'clicking on a file input element launches a file chooser');
</script>