code: private static TestingServer startLocalZooKeeper() throws Exception {
          // ZooKeeper is too noisy by default.
          ((Logger) LoggerFactory.getLogger("org.apache.zookeeper")).setLevel(Level.ERROR);
  
          // Start the testing server.
          TestingServer zooKeeperServer = new TestingServer(2181);
  
          // Configure EmoDB to use the testing server.
          System.setProperty("dw.zooKeeper.connectString", zooKeeperServer.getConnectString());
  
          return zooKeeperServer;
      }
docs: Start an in-memory copy of ZooKeeper.