Neos\Cache\Backend\TransientMemoryBackend::has PHP Method

    public function has($entryIdentifier)
    {
        return isset($this->entries[$entryIdentifier]);
    }

 /**
  * @test
  */
 public function flushRemovesAllCacheEntries()
 {
     $cache = $this->createMock(FrontendInterface::class);
     $backend = new TransientMemoryBackend($this->getEnvironmentConfiguration());
     $backend->setCache($cache);
     $data = 'some data' . microtime();
     $backend->set('TransientMemoryBackendTest1', $data);
     $backend->set('TransientMemoryBackendTest2', $data);
     $backend->set('TransientMemoryBackendTest3', $data);
     $backend->flush();
     $this->assertFalse($backend->has('TransientMemoryBackendTest1'), 'TransientMemoryBackendTest1');
     $this->assertFalse($backend->has('TransientMemoryBackendTest2'), 'TransientMemoryBackendTest2');
     $this->assertFalse($backend->has('TransientMemoryBackendTest3'), 'TransientMemoryBackendTest3');
 }