public function testConstructorAndIteration()
 {
     $group = $this->_getGroup();
     $group->add($this->_getField());
     $group->add($this->_getMultipleValueField());
     $fields = new RepeatableContainer($group);
     $fields->add();
     foreach ($fields as $key => $fieldGroup) {
         $this->assertEquals($group, $fieldGroup);
     }
     return $fields;
 }