public function test_adds_user_to_newsletter_list()
 {
     $curl = Mockery::mock(Curl::class);
     $curl->shouldReceive('post')->once()->andReturn('mocked');
     $newsLetter = new NewsLetter($curl);
     $out = $newsLetter->addToList('foo-list');
     $this->assertEquals($out, 'mocked');
 }