TestCase for URL Validation

I have below code with getter method and immutable object to get and parse URL :

class MyProg {
  private $url;   

  public function __construct($url) {

  $this->url = $url;

 }


public function getUrl() { 
            return $this->url;
     }

public function __toString() {
    return $this->url;
}

}

$c1 = new MyProg('http://www.google.com');

I am being told to create UNITTEST for all public method , Is it possible to create to Check Valid URL unit test for this page ? I have tried but havent found any.

Any help woulld be appreciated