chromium/third_party/blink/web_tests/clipboard/async-clipboard/clipboard-read-unsupported-types-removal.html

<!doctype html>
<meta charset="utf-8">
<title>Async Clipboard read unsupported types removal test.</title>
<body>Body needed for test_driver.click()</body>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script src="../../resources/testdriver.js"></script>
<script src="../../resources/testdriver-vendor.js"></script>
<script src="resources/user-activation.js"></script>
<script>
'use strict';

promise_test(async t => {
  await test_driver.set_permission({name: 'clipboard-read'}, 'granted');
  await waitForUserActivation();
  // Write supported and unsupported types to clipboard.
  document.addEventListener('copy', event => {
    event.clipboardData.setData('text/plain', 'Supported text.');
    event.clipboardData.setData('unsupported-type', 'Unsupported custom text.');
    event.preventDefault();
  });
  document.execCommand('copy');

  // Read clipboard contents.
  const clipboardItems = await navigator.clipboard.read();

  // The unsupported unsupported-type type should be removed, leaving only
  // the supported text/plain type.
  const clipboardItem = clipboardItems[0];
  assert_equals(clipboardItem.types.length, 1);
  assert_true(clipboardItem.types.includes('text/plain'));
  assert_false(clipboardItem.types.includes('unsupported-type'));
}, 'Verify that clipboard read removes unsupported types.');
</script>