chromium/third_party/blink/web_tests/editing/pasteboard/copy-cut-paste-keyevent.html

<!DOCTYPE html>
<html>
<head>
<title>Testing keydown with DomKey Cut, Copy and Paste</title>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
</head>
<body>
<input type="text" id="txt">
<script>
test(function() {
    assert_not_equals(window.eventSender, undefined, 'This test requires eventSender.');

    const txt = document.getElementById('txt');

    // Cut and Paste.
    txt.value = 'abc';
    txt.select();
    eventSender.keyDown('Cut');
    assert_equals(txt.value, '', 'Cut should delete selection');
    eventSender.keyDown('Paste');
    assert_equals(txt.value, 'abc', 'Should Paste Cut text');

    // Copy and Paste.
    txt.value = '123';
    txt.select();
    eventSender.keyDown('Copy');
    assert_equals(txt.value, '123', 'Copy shouldn\'t modify selection');
    eventSender.keyDown('Paste');
    eventSender.keyDown('Paste');
    assert_equals(txt.value, '123123', 'Should Paste twice');
}, "DomKey Cut, Copy and Paste should trigger corresponding edit actions");
</script>
</body>
</html>