jQuery Validation test on select-element

HTML

<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.11.1/jquery.validate.min.js"></script>
<form>
    <select required id="city">
        <option value="">Choose:</option>
        <option value="vanilla">Vanilla</option>
        <option value="chocolate">Chocolate</option>
    </select>
    <br>
    <input type="submit" />
</form>

JavaScript

$('#city').validate( {debug: true} );