如何为弹簧集成创建测试用例？

Question

我有一个ftp配置文件，例如

 public class FtpConfig {

    @Bean
    public DefaultFtpSessionFactory ftpSessionFactory() {
        DefaultFtpSessionFactory sessionFactory = new DefaultFtpSessionFactory();
        sessionFactory.setHost("host");
        sessionFactory.setPort(21);
        sessionFactory.setUsername("ftpuser");
        sessionFactory.setPassword("pass");
        return sessionFactory;
    }

@ServiceActivator(inputChannel = "fromFtpChannel")
    @Bean
    public FtpOutboundGateway getFiles() {
        FtpOutboundGateway gateway = new FtpOutboundGateway(ftpSessionFactory(), "get", "payload");
        gateway.setOptions(AbstractRemoteFileOutboundGateway.Option.STREAM.getOption());
        gateway.setOutputChannelName("fileoutput");
        return gateway;
    }
}

还有消息传递网关

@MessagingGateway
public interface ReadFilesGateway {
    @Gateway(requestChannel = "fromFtpChannel", replyChannel = "fileoutput")
    InputStream readFiles(String directory);
}

消息传递网关用于从ftp服务器下载文件，以输入流的形式查看文件。服务FileService使用网关读取文件。如何为服务或消息传递网关编写可能的测试用例？