java.lang.StackOverflowError while running junit test case

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 {
         assertEquals("video1", testObj.search("abcd"));

    }
}

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;  
                    }
                }
            }   
        }

I am not getting why java.lang.StackOverflowError error is coming . I am not expert at writing junit test cases Can someone please help to solve the error?