my custom plugin – updates post dates

HI peeps,
I have a client that has contracted me to make a plugin that essentially auto update the post dates weekly.

I decided to use modified_date to see if I can get that changed first. It checks daily and compares post dates and if it is over a week old it should update the date to this monday’s date.

I got pretty far with it but I am finding it hard to test.

add_action('my_daily_event', 'update_jobdate');

function check_updates() {
	if ( !wp_next_scheduled( 'update_jobdate' ) ) {
		wp_schedule_event( time(), 'daily', 'update_jobdate');
	}
}
add_action('wp', 'check_updates');

// do something everyday

	function update_jobdates(){
    global $wpdb;

//this monday
$this_monday = strtotime('Monday this week');
$newdate = $this_monday;
$newgmt_time = get_gmt_from_date($newdate);
$today = current_time('timestamp');
// Get all jobs

	$jobs_list = $wpdb->get_results("SELECT ID, post_date, post_modified, post_modified_gmt FROM $wpdb->posts WHERE cat = 'job_listing' AND post_status = 'publish' AND post_type = 'post'", ARRAY_A);

if ( $job_list ) {
    foreach ($job_list as $job_dates) {
        // Get current date
		$job_date = get_post_date( 'U' );
        // Get the days difference
		$difference = human_time_diff($job_date, $today);

        if ($difference >= "6 days") {

         // Update posts
  $my_post = array();
  $my_post['ID'] = '%s';
  $my_post['post_modified_gmt'] = '$newgmt_time';
  $my_post['post_modified'] = '$newdate';

// Update the post into the database
  wp_update_post( $my_post );

        }
		else {
			//do nothing
			 return false;
			}
    }
}
	}
add_action( 'wp' , 'update_jobdates' );
?>

Anything obvious?
And how do I test?

Thanks in advance guys.