public function testJsonSerialize()
 {
     $attendeeObject = new Attendee($this->responseArray);
     $attendeeJson = $attendeeObject->jsonSerialize();
     $this->assertArrayHasKey('firstName', $attendeeJson);
     $this->assertArrayHasKey('lastName', $attendeeJson);
     $this->assertArrayHasKey('email', $attendeeJson);
     $this->assertArrayHasKey('groupName', $attendeeJson);
 }