function testStrCmp()
 {
     $string1 = new SafeString('Big');
     $string2 = new SafeString('Bad');
     $this->assertEquals($string1->strcmp($string1, $string2), 1);
     $this->assertEquals($string1->strcmp($string2, $string1), -1);
     $this->assertEquals($string1->strcmp($string1, new SafeString('Big')), 0);
 }