woocommerce_order_status_completed action hook not working

I am developing woocommerce extension wher i need to perform some task after order is successfully completed. For that I started coding.
I used following code in constructor of my class.

add_action(‘woocommerce_order_status_completed’,array(&$this,’insert_points’));

Then I defined function as follows:

public function insert_points($order_id)
{
   global $woocommerce, $table_prefix;
   $order = new WC_Order($order_id);
   var_dump($order);
}

But it is not working.
Can anybody please help me using code sample.