protected function setUp()
 {
     $this->etag_hasher = $this->getMock(EtagHasherInterface::class);
     $this->em = $this->getMock(EntityManagerInterface::class);
     $this->doctrine = $this->getMockBuilder(Registry::class)->disableOriginalConstructor()->getMock();
     $this->builder = new CacheKeyBuilder($this->etag_hasher);
     $this->builder->setDoctrine($this->doctrine);
 }