public function testCopyPrivatePropertyFromSubClassObject()
 {
     $obj1 = new SubClass();
     $obj1->setPrivateProperty('Modified private property value of BaseClass');
     $obj2 = new BaseClass();
     $obj2->copyPrivateProperty($obj1);
     $this->assertEquals('Modified private property value of BaseClass', $obj2->getPrivateProperty());
     $obj3 = new SubClass();
     $obj3->copyPrivateProperty($obj1);
     $this->assertEquals('Modified private property value of BaseClass', $obj3->getPrivateProperty());
 }