Beginner JQUERY help: "wp_enqueue_script was called incorrectly"

Hi all. I’m trying to include and run a simple Javascript file on my site, but am encountering an error. My debug.log file reads:

PHP Notice:  wp_enqueue_script was called <strong>incorrectly</strong>. Scripts and styles should not be registered or enqueued until the <code>wp_enqueue_scripts</code>, <code>admin_enqueue_scripts</code>, or <code>login_enqueue_scripts</code> hooks. Please see <a href="http://codex.wordpress.org/Debugging_in_WordPress">Debugging in WordPress</a> for more information. (This message was added in version 3.3.) in /home/artslamm/public_html/wp-includes/functions.php on line 3547

I’m not sure what this means. Can anyone shed some light?

Here are the steps I carried out.

The script consists of one line only:

alert('Hello, World!')

and is in a file ‘test.js,’ which resides in the same directory as my functions.php file.

To add this script to WordPress, I inserted the following code into my functions.php file:

function add_test_script() {
    wp_enqueue_script(
        'test', // name your script so that you can attach other scripts and de-register, etc.
      get_template_directory_uri() . 'test.js', // this is the location of your script file
        array('jquery') // this array lists the scripts upon which your script depends
    );
}
add_action( 'wp_enqueue_scripts', 'add_test_script' );

Thanks in advance.