chromium/third_party/blink/web_tests/fast/forms/color-scheme/autofill/autofilled.html

<!DOCTYPE html>
<meta name="color-scheme" content="light dark">

This tests the appearance of autofilled inputs, textareas, and select options.<br>
<form>
    <input type="text" value="Text field">
    <input type="search" value="Search value">
    <textarea>Textarea</textarea>
    <select>
        <option selected>Option 1</option>
        <option >2</option>
        <option>autofilled</option>
    </select>
    <select></select>
</form>
<style>
  form > * {display: block;}
</style>
<script>
  window.onload = () => {
    if (window.internals) {
      document.querySelectorAll('form > *').forEach(c => {
        internals.setAutofilledValue(c, "autofilled");
        internals.setAutofilled(c, true)
      });
    }
  }
</script>