如何对包含I / O文件的Netty处理程序进行单元测试？

Question

in channelRead of the channelhandleradapter i am writing to a file , i know how to use embeddedchannel to unit test netty handlers , but how to unit test this handler when we are doing file I/O inside it(ChannelRead) ? something like mock with no i/O file dependency .

public class LogHandler : ChannelHandlerAdapter
   {

       const string Path = @"L:\Log.txt";
        public override void ChannelActive(IChannelHandlerContext context)
        {
            base.ChannelActive(context);
        }

        public override Task WriteAsync(IChannelHandlerContext context, object message)
        {
            Logger.SentLog(message as IByteBuffer);
            return context.WriteAsync(message as IByteBuffer);
        }

        public override void ChannelRead(IChannelHandlerContext context, object message)
        {

            string msg = Convertor.ByteBufferToString(message as IByteBuffer);
            IByteBuffer initialMessage = Unpooled.Buffer(1024);
            byte[] messageBytes = Encoding.UTF8.GetBytes(msg);
            initialMessage.WriteBytes(messageBytes);


            using (StreamWriter writer = new StreamWriter(Path, true))
            {
                writer.WriteLine($"(Read){System.DateTime.Now} -> {BitConverter.ToString(messageBytes).Replace("-"," ")}");
            }

            if (msg != "Timeout")
            {
                base.ChannelRead(context, message);
            }

        }
}

Answer 1

You class depends on the StreamWriter class. You need to change your class in such way that you provide these dependency from the caller and that you can mock it in your unit tests. Therefore, you could create a simple wrapper class for the StreamWriter instantiation, use this wrapper class in your class and inject it in the constructor/ per setter. And in your unit test setup up the mock to return a local StreamWriter that you can use to verify the content written.

Answer 2

You can still use EmbeddedChannel . Just use writeInbound(...) and verify it returns false . Then once you called channel.finish() verify what was written in the file.