Neos\Flow\Log\Logger::addBackend PHP Method

    public function addBackend(Backend\BackendInterface $backend)
    {
        $this->backends->attach($backend);
        $backend->open();
    }

 /**
  * @test
  */
 public function theShutdownMethodRunsCloseOnAllRegisteredBackends()
 {
     $mockBackend1 = $this->getMockBuilder(BackendInterface::class)->setMethods(['open', 'append', 'close'])->getMock();
     $mockBackend1->expects($this->once())->method('close');
     $mockBackend2 = $this->getMockBuilder(BackendInterface::class)->setMethods(['open', 'append', 'close'])->getMock();
     $mockBackend2->expects($this->once())->method('close');
     $logger = new Logger();
     $logger->addBackend($mockBackend1);
     $logger->addBackend($mockBackend2);
     $logger->shutdownObject();
 }