I am using bootstrap-select for a form. I include the scripts (jquery, bootstrap-select) in the header of the HTML file.

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/css/bootstrap-select.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/js/bootstrap-select.min.js"></script>
<link rel="stylesheet "type="text/css" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

All the select elements with class "selectpicker" all called correctly. Example of the select element:

<select id="test" class="selectpicker">
        <option>Mustard</option>
        <option>Ketchup</option>
        <option>Relish</option>
</select>

However, if I call the following script on the same page

<script>
$(document).ready(
    function () {
        $('#test').selectpicker('val', 'Relish')
});
</script>

I get this nasty error

$(...).selectpicker is not a function

Looking at the sources tab in Google Chrome, I see that the bootstrap-select.min.js is loaded well. Has anyone got suggestions?