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chromium/third_party/blink/web_tests/fast/forms/validation-bubble-appearance-edge.html 

<!DOCTYPE html>
<meta name="color-scheme" content="light dark">
<p>Check if a validation bubble is shown at a correct position.</p>
<input pattern="\d{4}" title="Please specify four digits." value="abc" style="position:absolute; right:8px; bottom: 8px;">
<script>
document.querySelector('input').reportValidity();
</script>