Java Chat Server（Socket）-如何编写单元测试？

Question

I have written a Java Chat Server program. This is a simple standalone program for Server. I have to run this then run Client to get Chat working. What are some possible Unit Test scenarios for the server program? Can anyone show me some example of unit test based on this code? I have never written a unit test code before and I can't really think of what needs to be tested here.. I think testing Connection can be one but what else? (and how to?)

public class SimpleChatServer {

    static final Logger logger = LogManager.getLogger(SimpleChatServer.class);      
    ArrayList<PrintWriter> clientOutputStreams;
    private BufferedReader reader;
    private Socket sock;
    private ServerSocket serverSock;

    public class ClientHandler implements Runnable{

        public ClientHandler(Socket clientSocket){  // Socket Connection
            try {
                sock = clientSocket;
                InputStreamReader isReader = new InputStreamReader(sock.getInputStream());
                reader = new BufferedReader(isReader);
            } catch(Exception ex) {
                logger.trace(ex);
            }
        }

            public void run() {
                String message;
                try {
                    while ((message = reader.readLine()) != null) {
                        System.out.println("read " + message);
                        tellEveryone(message);
                    }
                } catch(Exception ex) {
                    logger.trace(ex);
                }
            } //close run

    } //close ClientHandler

        public static void main (String[] args) throws Exception
        {
            new SimpleChatServer().listen();
        }

        @SuppressWarnings("resource")
        public void listen()
        {
            clientOutputStreams = new ArrayList<PrintWriter>();
            try {

                ServerSocket serverSock = new ServerSocket(8000); //port number 8000 was used
                while(true) {
                    Socket clientSocket = serverSock.accept();
                    PrintWriter writer = new PrintWriter(clientSocket.getOutputStream());
                    clientOutputStreams.add(writer);

                    Thread t = new Thread(new ClientHandler(clientSocket));
                    t.start();
                }
            } catch (Exception ex) {
                logger.trace("Server Error", ex);
            } finally {
                try
                {
                    serverSock.close();
                }
                catch(Exception e){}
            }

        } // close go

        public void tellEveryone(String message)
        {
            Iterator<PrintWriter> it = clientOutputStreams.iterator();
            while(it.hasNext()) {
                try {
                    PrintWriter writer = (PrintWriter) it.next();
                    writer.println(message);
                    writer.flush();
                } catch (Exception ex) {
                    logger.trace(ex);
                }
            } // end while
        } // close tellEveryone

}

Answer 1

I was going to crib an answer from Pragmatic Unit Testing , but suggest you just find a copy. At the very least you should consider whether results are right, whether your boundary conditions are correct, and if you can force error conditions.

Testing results often means making sure combinations of input get the expected results. Boundaries are reflected in the related "0, 1, many" rule, where you do silly stuff to see if your code has implicit boundaries that can be reached with bad, null or unexpected values.

For example, what happens if you pass huge Strings to your methods that take them? What about strings with weird Unicode chars in them? No line breaks?

Forcing error conditions means making sure things degrade gracefully and/or throw under the expected situation.

Think about your code as a brittle little appliance and then pretend a poo-flinging monkey, a 14-yr old hacker and your non-hacker grandmother (I know some exist) are all taking turns on it.