chromium/third_party/blink/web_tests/fast/forms/text/input-appearance-autocomplete-suggested-value-over-placeholder-value.html

<input id="input" placeholder="City">
<script>
// Make sure that the placeholder is not in visible mode when a suggested value
// replaces a visible placeholder value
internals.setSuggestedValue(input, 'Springfield');
</script>
<style>
:placeholder-shown {
background-color: red;
}
</style>