public function testRemove()
 {
     /** @var NotificationInterface $notification */
     $notification = $this->getMock(NotificationInterface::class);
     $this->objectManager->expects($this->at(0))->method('remove')->with($notification);
     $this->objectManager->expects($this->at(0))->method('flush');
     $result = $this->mapper->remove($notification);
     $this->assertTrue($result);
 }