public function testHasChildren()
 {
     $view = new AphrontNullView();
     $this->assertFalse($view->hasChildren());
     $values = array(null, '', array(), array(null, ''));
     foreach ($values as $value) {
         $view->appendChild($value);
         $this->assertFalse($view->hasChildren());
     }
     $view->appendChild('!');
     $this->assertTrue($view->hasChildren());
 }