Java IO, inputstream and Outputstream testing

Question

I am trying to create a simple chat program.
Initially I wrote this code to save an input message from user into a Text file, depending on the given Command, but I don't have any idea about the testing strategy. Should I write test for the runUi() only? Because this method already contains switch statement and inside it are the other methods invoked, or should I write for all other methods as well?

public class CmdLineUI implements ChatUI, Chat {
    public static final String WRITE = "write";
    public static final String READ = "read";
    public static final String EXIT = "exit";
    public static final String ERRORMESSAGE = "unknown command";

    private final PrintStream consoleOutput;
    private final BufferedReader userInput;

    public CmdLineUI(PrintStream os, InputStream is) {
        this.consoleOutput = os;
        this.userInput = new BufferedReader(new InputStreamReader(is));
    }

    public static void main(String[] args) throws Exception {
        PrintStream os = System.out;
        os.println("***Welcome to The ChatSystem:  input: write for chatting ,"
                + "\n    for Reading the messages input: read ,for closing Chat input: exit ***");

        CmdLineUI userCmd = new CmdLineUI(os, System.in);

        userCmd.runUi(System.in, os);
    }



    private String[] readCommands() throws Exception {
        String[] result = new String[1];
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        String commandLinString = null;
        String command = null;

        try {
            System.out.println("> ");

            commandLinString = br.readLine();
            StringTokenizer st = new StringTokenizer(commandLinString);
            command = st.nextToken().trim();
            // msg = st.nextToken();

            System.out.println("command :" + command);
        } catch (IOException e) {
            System.out.println("Exception when reading from comman line" + e.getLocalizedMessage());
        }
        result[0] = command;
        // result[1] = msg;

        return result;
    }

    @Override
    public void writeMessage(String message) throws Exception {
        System.out.println("Start with Writing mood:");

        try {
            File file = new File("/home/sami/Desktop/file.txt");
            InputStreamReader inputStreamReader = new InputStreamReader(System.in); // A stream for reading from the
                                                                                    // console
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader); // Connect InputStreamReader to a
                                                                                    // BufferedReader
            FileWriter fileReader = new FileWriter(file); // A stream that connects to the text file
            BufferedWriter bufferedWriter = new BufferedWriter(fileReader); // Connect the FileWriter to the
                                                                            // BufferedWriter
            String line;
            boolean continuee = true;

            while (!(line = bufferedReader.readLine()).equals("stop")) {
                continuee = false;
                bufferedWriter.write(line);
            }
            // Close the stream
            bufferedWriter.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    @Override
    public void readMessage() throws Exception {
        System.out.println("start with reading mood:");

        File file = new File("/home/sami/Desktop/file.txt");
        FileInputStream fileinputstream = new FileInputStream(file);

        try {
            int oneByte;
            while ((oneByte = fileinputstream.read()) != -1) {
                System.out.write(oneByte);
            }

            System.out.flush();
        } catch (Exception ex) {
            ex.getMessage();
        }

        fileinputstream.close();
    }

    @Override
    public void runUi(InputStream inp, OutputStream outp) throws Exception {
        File file = new File("/home/sami/Desktop/file.txt");
        FileReader filereader = new FileReader(file);
        BufferedReader br = new BufferedReader(filereader);

        // CmdLineUI obj = new CmdLineUI(consoleOutput);
        PrintStream ps = new PrintStream(outp);
        boolean again = true;

        while (again) {
            String[] commandMsg = readCommands();
            String command = commandMsg[0];

            switch (command) {
            case WRITE:
                writeMessage(br.readLine());
                again = true;
                break;

            case READ:
                readMessage();
                again = true;
                break;

            case EXIT:    
                again = false;
                break;

            default:
                ps.println(ERRORMESSAGE);
            }
        }

    }

}

and I have created these two interfaces here is the first one

public interface ChatUI {
    public void runUi (InputStream inp, OutputStream outp) throws Exception;
}

the second Interface

public interface Chat {
     //First Method 
    public void writeMessage(String message)throws Exception;

    // Second Method
    public void readMessage()throws Exception;
}

Answer 1

Write tests for your runUi() method because in all the other methods, you are either reading from console and tokenizing the input String , writing to a file or reading from a file. All of these 3 operations have already been tested by folks at Oracle and/or the Java language developers (you can google about this process if you want to know more).

Check to see if your program flow is working as expected and write tests for them and don't bother with the functions where all you are doing is calling come Java API and then doing almost nothing except for returning (or writing to somewhere) from it.

Answer 2

I wrote this program again using different way, and I have tested the Methods also:

import java.io.*;
import java.util.*;

public class CmdLineUI implements ChatUI, Chat {

    public static final String WRITE = "write";
    public static final String READ = "read";
    public static final String EXIT = "exit";
    public static final String ERRORMESSAGE = "unknown command";

    private BufferedReader userInput;

    public static void main(String[] args) throws Exception {
        PrintStream os = System.out;
        os.println("***Welcome to The ChatSystem:  input: write for chatting ,"
                + "\n    for Reading the messages input: read ,for closing Chat input: exit ***");

        CmdLineUI userCmd = new CmdLineUI();

        userCmd.runUi(System.in, System.out);

    }

    @Override
    public void writeMessage(String message) throws Exception {
        System.out.println("Start with Writing mode:");
        try {
            File file = new File("/home/sami/Desktop/file.txt");
            InputStreamReader inputStreamReader = new InputStreamReader(System.in); // A stream for reading from the
                                                                                    // console
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader); // Connect InputStreamReader to a
                                                                                    // BufferedReader

            FileWriter fileReader = new FileWriter(file); // A stream that connects to the text file
            BufferedWriter bufferedWriter = new BufferedWriter(fileReader); // Connect the FileWriter to the
                                                                            // BufferedWriter

            String line;
            boolean continuee = true;
            while (!(line = bufferedReader.readLine()).equals("stop")) {
                continuee = false;
                bufferedWriter.write(line);
            }

            // Close the stream
            bufferedWriter.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    @Override
    public void readMessage() throws Exception {
        System.out.println("start with reading mode:");
        File file = new File("/home/sami/Desktop/file.txt");

        BufferedReader br = new BufferedReader(new FileReader(file));
        try {
            String oneByte;
            while ((oneByte = br.readLine()) != null) {
                System.out.println(oneByte);
            }

        }

        catch (Exception ex) {
            ex.getMessage();
        }

    }

    @Override
    public void runUi(InputStream inp, OutputStream outp) throws IOException {
        this.userInput = new BufferedReader(new InputStreamReader(inp));

        BufferedReader br = new BufferedReader(userInput);
        PrintStream ps = new PrintStream(outp);

        CmdLineUI userCmd = new CmdLineUI();

        String commandLinString = null;
        boolean again = true;
        try {
            while (again) {

                System.out.println("> ");
                commandLinString = br.readLine().trim();
                StringTokenizer st = new StringTokenizer(commandLinString);
                String command = st.nextToken();
                // String msg= userCmd.readCommands(command);
                System.out.println("command :" + command);
                switch (command) {

                case WRITE:

                    writeMessage(command);
                    again = true;
                    break;

                case READ:

                    readMessage();

                    again = true;
                    break;
                case EXIT:

                    again = false;
                    break;
                default:
                    ps.println(ERRORMESSAGE);
                }

            }

        } catch (Exception e) {
            System.out.println("Exception when reading from comman line" + e.getLocalizedMessage());

        }

    }

}

And Here is the Test:

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.Test;

import junit.framework.Assert;

import java.io.*;

class CmdTesting {



    @Test
    void test() throws Exception {
        try {
            CmdLineUI obj = new CmdLineUI();

            InputStream myInputStream = null;

            String unknownCommandString = "hello world";
            String exitString = CmdLineUI.EXIT;

            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            DataOutputStream dos = new DataOutputStream(baos);
            dos.writeUTF(unknownCommandString);

            byte[] inputBytes = baos.toByteArray();

            ByteArrayInputStream bais = new ByteArrayInputStream(inputBytes);
            myInputStream = bais;

            ByteArrayOutputStream myOutputStream = new ByteArrayOutputStream();

            obj.runUi(myInputStream, myOutputStream);

            ByteArrayInputStream outputIS = new ByteArrayInputStream(myOutputStream.toByteArray());

            DataInputStream dis = new DataInputStream(outputIS);

            dis.readUTF();

            String expected = "hello world";

            assertEquals(expected, unknownCommandString);

        } catch (Exception ex) {
            ex.getLocalizedMessage();
        }

    }

    @Test
    public void writeMessage() throws Exception {

        File file = new File("/home/sami/Desktop/file.txt");
        String str = "Hello";

        BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));
        writer.append(' ');
        writer.append(str);

        writer.close();
    }


    @Test
    public void reamessage() throws Exception {
        File file=new File("/home/sami/Desktop/file.txt");

        BufferedReader reader = new BufferedReader(new FileReader(file));
        reader.read();
    }
}