chromium/third_party/blink/web_tests/editing/pasteboard/data-transfer-items-image-png-details.html

<!DOCTYPE html>
<title>Clipboard: getAsFile() returns File for image</title>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<style>
  .hidden { display: none; }
</style>
<div id=instructions class=hidden>
  This file tests the image pasting functionality of
  DataTransferItems. To try the test manually, right-click on the
  image &gt; Copy Image, click anywhere in the background of the main
  page and paste.
</div>
<iframe id="src" src="resources/mozilla.gif"></iframe><br>
<script>
async_test(t => {
  window.addEventListener('load', () => {
    document.body.addEventListener('paste', t.step_func(e => {
      const items = e.clipboardData.items;
      assert_true(Array.from(items).some(i => i.kind === 'file'),
                  'A file should be present in the data');
      for (let i = 0; i < items.length; ++i) {
        if (items[i].kind == 'file') {
          const file = items[i].getAsFile();
          assert_class_string(file, 'File', 'IDL type should be File');
          assert_equals(file.type, 'image/png', 'MIME type should be PNG');
          assert_equals(file.name, 'image.png', 'File name should be generic');

          // Allow for clock skew between script engine and DOM, NTP
          // updates, slow test bots, etc. See https://crbug.com/324110
          const slop_ms = 60 * 60 * 1000;
          assert_approx_equals(file.lastModified, Date.now(), slop_ms,
                               'Should be newish');
          t.done();
          return;
        }
      }
    }));

    try {
      const srcElement = document.getElementById('src');
      srcElement.contentWindow.document.execCommand('copy');
      document.execCommand('paste');
    } catch (ex) {
      // Fails in browser due to cross-origin restriction when run
      // locally via file: so show manual instructions.
      document.body.querySelector('#instructions').classList.remove('hidden');
    }
  });
}, 'DataTransferObject.getAsFile() returns File for image pastes');
</script>