Unit Test For Infinite Loop

Question

This is my java thread run method and i want to write unit test for this method. But with infinte loop i can not do it. It would be nice anyone can help me with this.

 public void run() {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String line = null;
        boolean oneTime = true;
        loadDescription();
        while (true) {

            try {
                if (oneTime) {
                    System.out.println("press enter to get the console...............");
                    oneTime = false;
                }
                line = in.readLine();
                if (line != null) {
                    processInput(line);
                }

            } catch (Exception e) {
                logger.error("Error occurred while processing console");
                logger.error(e.getMessage(), e);
            }
        }
    }

this is loadDescription() method

private void loadDescription() {
        BufferedReader in = null;
        StringBuffer stringBuffer = null;
        String str = null;
        try {
            stringBuffer = new StringBuffer();
            in = new BufferedReader(new FileReader(IConstants.MANUAL_FILE));
            str = in.readLine();
            while (str != null) {
                stringBuffer.append(str + "\n");
                str = in.readLine();
            }
            dfixDescription = stringBuffer.toString();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);  //To change body of catch statement use File | Settings | File Templates.
        } finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (IOException e) {
                logger.error(e.getMessage(), e);  //To change body of catch statement use File | Settings | File Templates.
            }
        }
    }

and

private void processInput(String line) {
        line = line.trim();
        logger.info("Admin Message received: " + line);
        if ("?".equalsIgnoreCase(line) || "".equals(line)) {
              printDescription();
        } else if (line.toUpperCase().startsWith(AdminCommands.RELOAD)) {
            loadDescription();
            printDescription();
        } else if (line.toUpperCase().startsWith(AdminCommands.EXIT)) {
            adminManager.stopDFIXRouter();
            logger.debug("Closing Application.....");
            logger.debug("Closed.");
            System.exit(0);
        } else if (line.toUpperCase().startsWith(AdminCommands.RESET_OUT_SEQUENCE)) {
            try {
                String sessionIdentifier = line.split(",")[1].trim();
                int seqNo = Integer.parseInt((line.split(",")[2]).trim());
                adminManager.resetOutSequence(sessionIdentifier, seqNo);
            } catch (Exception e) {
                logger.error(e.getMessage(), e);  //To change body of catch statement use File | Settings | File Templates.
            }
        } else if (line.toUpperCase().startsWith(AdminCommands.RESET_IN_SEQUENCE)) {
            try {
                String sessionIdentifier = line.split(",")[1].trim();
                int seqNo = Integer.parseInt((line.split(",")[2]).trim());
                adminManager.resetInSequence(sessionIdentifier, seqNo);
            } catch (Exception e) {
                logger.error(e.getMessage(), e);  //To change body of catch statement use File | Settings | File Templates.
            }
        } else if (line.toUpperCase().startsWith(AdminCommands.CONNECT)) {
            String sessionIdentifier = line.split(",")[1].trim();
            adminManager.connectSession(sessionIdentifier);
        } else if (line.toUpperCase().startsWith(AdminCommands.DISCONNECT)) {
            String sessionIdentifier = line.split(",")[1].trim();
            adminManager.disconnectSession(sessionIdentifier);
        } else if (line.toUpperCase().startsWith(AdminCommands.ACTIVATE)) {
            adminManager.startDFIXRouter();
        } else if (line.toUpperCase().startsWith(AdminCommands.PASSIVATE)) {
            adminManager.stopDFIXRouter();
        } else if (line.toUpperCase().startsWith(AdminCommands.RUN_EOD)) {
            try {
                String sessionIdentifier = line.split(",")[1].trim();
                adminManager.runEod(sessionIdentifier);
            } catch (Exception e) {
                logger.error(e.getMessage(), e);  //To change body of catch statement use File | Settings | File Templates.
            }
        } else if (line.toUpperCase().startsWith(AdminCommands.SHOW_STATUS)) {
            adminManager.showStatus();
        } else {
            System.out.println("Usage: type ? for help");
        }
        System.out.print(">");
    }

and these are related methods for run method. following is my test method

 @Test
    public void run_activate() throws Exception{

        String data = "activate";
        InputStream in = new ByteArrayInputStream(data.getBytes());
        System.setIn(in);
        PowerMockito.mockStatic(AdminManager.class);
        PowerMockito.when(AdminManager.getInstance()).thenReturn(adminManagerTest);
        Mockito.doNothing().when(adminManagerTest).startDFIXRouter();
        dfixrtrAdminTest.run();
        Mockito.verify(adminManagerTest, Mockito.times(1)).startDFIXRouter();

    }

what is wrong with this. When i run test method it will not stop and i can not verify that needed methods are invoked how to handle this.

Answer 1

You need to replace the code inside the infinite loop with a function.

You then write a unit test for that function.

Answer 2

Obviously you can't test if a loop is really "infinite".

But then you can still step back and look at all the details this method is doing, like:

• opening a reader from which it will read
• having that special condition that ensures that "something" happens only once

In other words: as usually with unit tests, you carefully think about the different paths that your code can take (think: "white box testing"). That can tell you about test cases required to hit corner cases. On the other hand, you should also look at the public contract of your method (black box testing) - what are the things that you expect this method to do, without knowing about its implementation. That is how you think about your code, in order to then come up with reasonable tests.

And beyond that: your example is bogus. There shouldn't be an infinite loop here - at some point all lines will be read, and read() will not return anything else but null.