java.lang.StackOverflowError while running junit test case

Question

I am writing junit test cases for a java application Here is junit test code

public class CultureMachineTestCases extends CultureMachineAssignment {

    CultureMachineTestCases testObj=new CultureMachineTestCases();

    @Before
    public void init() throws IOException{
        testObj.insertDataIntoSet();
        testObj.addKeywords("video1");

    }

    /*@Test
public void testVideo() throws IOException {
    result=testObj.search("abcd");
    answer=result.toString();
    answer1=answer.replaceAll("[^a-z0-9]","");

     assertEquals("video1", answer1);

}
@Before
public void initMethod() throws IOException{
    testObj.insertDataIntoSet();
    testObj.addKeywords("video2");
 }   */ @Test
  public void testLenth() throws IOException{
    flagVal=testObj.flag;

    assertEquals(1, flagVal);

    }
}

After I run this code in eclipse I am getting following error

 java.lang.StackOverflowError
    at cultureMachine.CultureMachineAssignment.<init>     (CultureMachineAssignment.java:13)
    at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:11)
     at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:14)
     at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:14)
    at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:14)
 java.lang.StackOverflowError
    at cultureMachine.CultureMachineAssignment.<init>     (CultureMachineAssignment.java:13)
    at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:11)
    at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:14)
    at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:14)
    at cultureMachine.CultureMachineTestCases.<init>(CultureMachineTestCases.java:14)

Here is my main java code

package cultureMachine;
        public class CultureMachineAssignment {

            HashMap<String,HashSet<String>> kewordVideo = new HashMap<String,HashSet<String>>();
            HashMap<String,HashSet<String>> videoKeyword =  new         HashMap<String,HashSet<String>>();
            HashMap<String,Integer> keywordLength = new HashMap<String,Integer>();

            HashSet<String> videoNames = new HashSet<String>();
            HashSet<String> result = new HashSet<String>();

            public void insertDataIntoSet(){
                for(int i=0;i<500;i++){
                    videoNames.add("video"+i);
                }
            }
            public void addKeywords(String video)throws IOException{


                InputStreamReader ip = new InputStreamReader(System.in);
                BufferedReader br = new BufferedReader(ip);

                Integer previousVal=0;

                if(!videoKeyword.containsKey(video) && videoNames.contains(video)){
                    videoKeyword.put(video,new HashSet<String>());
                }
                else if(!videoNames.contains(video)){
                    System.out.println("Video is not a part of lookup");
                }

                System.out.println("Enter keywords for video");
                String keyword =br.readLine();

                if(!keywordLength.containsKey(video))
                    keywordLength.put(video, 0);

                if((keywordLength.get(video)+keyword.length())<500){
                    videoKeyword.get(video).add(keyword);
                    previousVal=keywordLength.get(video);
                    keywordLength.put(video, previousVal+keyword.length());
                }
                else{
                    System.out.println("Maximum length exceeded for video "+ video);
                }
                if(!kewordVideo.containsKey(keyword)){
                    kewordVideo.put(keyword,new HashSet<String>());
                }
                kewordVideo.get(keyword).add(video);
            }

            public HashSet search(String searchKey){
                for (Entry<String, HashSet<String>> entry : videoKeyword.entrySet()) {
                    for (String s : entry.getValue()) {
                        if (s.contains(searchKey)) {
                            result.add(entry.getKey());
                        break;
                        }
                    }
                }
                return result;
            }

            public static void main(String args[]) throws IOException {

                CultureMachineAssignment obj1 = new CultureMachineAssignment();
                HashSet<String> searchResults = new HashSet<String>();
                int num=0;
                InputStreamReader ip = new InputStreamReader(System.in);
                BufferedReader br = new BufferedReader(ip);
                obj1.insertDataIntoSet();
                Scanner in = new Scanner(System.in);
                while(num!=3){
                    System.out.println();
                    System.out.println("Please enter your choice");
                    System.out.println("1. To assign keyword to video");
                    System.out.println("2. To Search Video using keyword");
                    System.out.println("3. Exit");

                    num=in.nextInt();

                    switch(num)
                    {
                    case 1 :
                        System.out.println("Enter Video name[video followed by video number]");
                        String video =br.readLine();
                        if(obj1.videoNames.contains(video))
                            obj1.addKeywords(video);
                        else
                            System.out.println(video+" is not a part of lookup");
                        break;
                    case 2 :
                        System.out.println("Enter partial or complete keyword to search video");
                        String searchKey = br.readLine();
                        searchResults=obj1.search(searchKey);
                        System.out.println(searchResults);
                        break;  
                    case 3:
                        System.out.println("exiting from application");
                        break;  
                    default:
                        System.out.println("Please enter correct choice");
                        break;  
                    }
                }
            }   
        }

Can someone please help to solve the error? Here I am not able to run both test function individually they are running fine How to run them together

Answer 1

Your testcase should not extend the object you would like to test:

public class CultureMachineTestCases{

    CultureMachineAssignment testObj=new CultureMachineAssignment ();

    @Before
    public void init() throws IOException{
        testObj.insertDataIntoSet();
        testObj.addKeywords("video1");

    }

    @Test
    public void testVideo() throws IOException {
         assertEquals("video1", testObj.search("abcd"));

    }
}

If you run the testcase, a new object of CultureMachineTestCases is created which will also create an instance of object CultureMachineTestCases and so on. That's why you get the StackOverflowException .

Answer 2

My favorite error, you have an recurring code, that never ends, and after entering the same method all and all again it throw StackOverflow.

It is because you instantiate CultureMachineTestCases, which has a field that instantiate CultureMachineTestCases, and so on... you have recurring instatntiation, when the object is constructed it constructs another one inside itself, and this makes next, and so on...