public function itOnlyLogsErrorsAndWarningsInTheLogStack()
 {
     expect($this->backend_logger)->log()->count(4);
     $this->logger->error("this is an error");
     $this->logger->warn("this is a warning");
     $this->logger->info("this is an info");
     $this->logger->debug("this is a debug");
     $expected_logs = array("[error] this is an error", "[warning] this is a warning");
     $this->assertEqual($this->logger->getAllLogs(), $expected_logs);
 }