private String mockNewConnection(String host, Port port) {
    // mocks selector connect.
    String connId = host + port.getPort() + connStringIndex++;
    connIds.add(connId);
    return connId;
  }
Mocks a {@link Selector#connect(java.net.InetSocketAddress, int, int, PortType)} call.
@param host the host to connect to
@param port the port to connect to
@return return newly made connection.
ambry-network/src/test/java/com/github/ambry/network/ConnectionTrackerTest.java