LayoutTests/fast/forms/input-text-drag-down.html

<input type="text" value="This is a bunch of text.">
<p>Tests drag-selecting down. If the test succeeds, the text from the center to the end of the text field should be selected.</p>
<script>
onload = async () => {
    if (!window.testRunner)
        return;

    testRunner.waitUntilDone();
    if (window.eventSender) {
        await eventSender.asyncMouseMoveTo(50, 15);
        await eventSender.asyncMouseDown();
        await eventSender.asyncMouseUp();
        await eventSender.asyncMouseDown();
        await eventSender.asyncMouseMoveTo(50, 40);
        await eventSender.asyncMouseUp();
    }
    testRunner.notifyDone();
}
</script>