mozilla-release/testing/web-platform/tests/clipboard-apis/async-write-text-read-blobtext-manual.https.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Async Clipboard writeText -> read (text/plain Blob) tests</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
async function readWriteTest(textInput) {
  promise_test(async t => {
    await navigator.clipboard.writeText(textInput);
    const blobOutput = await navigator.clipboard.read();
    assert_equals(blobOutput.type, "text/plain");

    const textOutput = await (new Response(blobOutput)).text();
    assert_equals(textOutput, textInput);
  }, "Verify write and read clipboard given text: " + textInput);
}

readWriteTest("Clipboard write text -> read (text/plain Blob) test");
readWriteTest("non-Latin1 text encoding test データ");
</script>
<p>
  Note: This is a manual test because it writes/reads to the shared system
  clipboard and thus cannot be run async with other tests that might interact
  with the clipboard.
</p>