public function testFilterCallback()
 {
     $admins = $this->objFromFixture('Group', 'admingroup');
     $field = new ManyManyPickerField($admins, 'Members', 'Member', array('FilterCallback' => create_function('$i', 'return $i->FirstName != "Admin";')));
     $this->assertDOSContains(array(array('FirstName' => 'All Group User')), $field->Items());
 }