protected function prepareSubscriber(Subscriber $subscriber)
 {
     $subscriber->getEmail()->willReturn('*****@*****.**');
     $subscriber->getMergeTags()->willReturn(['FIRSTNAME' => 'Charles']);
 }
 public function unsubscribe($listId, Subscriber $subscriber)
 {
     $this->mailchimp->lists->unsubscribe($listId, ['email' => $subscriber->getEmail()], true, false, false);
 }