#vulnerable code 
                              @Test
  public void testSimpleCS() {
    // setup resource
    Map<String, Resource> resourceMap = getResourceMap();

    setupLiveInstances(5);

    event.addAttribute(AttributeName.RESOURCES.name(), resourceMap);
    CurrentStateComputationStage stage = new CurrentStateComputationStage();
    runStage(event, new ReadClusterDataStage());
    runStage(event, stage);
    CurrentStateOutput output1 = event.getAttribute(AttributeName.CURRENT_STATE.name());
    AssertJUnit.assertEquals(
        output1.getCurrentStateMap("testResourceName", new Partition("testResourceName_0")).size(),
        0);

    // Add a state transition messages
    Message message = new Message(Message.MessageType.STATE_TRANSITION, "msg1");
    message.setFromState("OFFLINE");
    message.setToState("SLAVE");
    message.setResourceName("testResourceName");
    message.setPartitionName("testResourceName_1");
    message.setTgtName("localhost_3");
    message.setTgtSessionId("session_3");

    Builder keyBuilder = accessor.keyBuilder();
    accessor.setProperty(keyBuilder.message("localhost_" + 3, message.getId()), message);

    runStage(event, new ReadClusterDataStage());
    runStage(event, stage);
    CurrentStateOutput output2 = event.getAttribute(AttributeName.CURRENT_STATE.name());
    String pendingState =
        output2.getPendingState("testResourceName", new Partition("testResourceName_1"),
            "localhost_3").getToState();
    AssertJUnit.assertEquals(pendingState, "SLAVE");

    ZNRecord record1 = new ZNRecord("testResourceName");
    // Add a current state that matches sessionId and one that does not match
    CurrentState stateWithLiveSession = new CurrentState(record1);
    stateWithLiveSession.setSessionId("session_3");
    stateWithLiveSession.setStateModelDefRef("MasterSlave");
    stateWithLiveSession.setState("testResourceName_1", "OFFLINE");
    ZNRecord record2 = new ZNRecord("testResourceName");
    CurrentState stateWithDeadSession = new CurrentState(record2);
    stateWithDeadSession.setSessionId("session_dead");
    stateWithDeadSession.setStateModelDefRef("MasterSlave");
    stateWithDeadSession.setState("testResourceName_1", "MASTER");

    accessor.setProperty(keyBuilder.currentState("localhost_3", "session_3", "testResourceName"),
        stateWithLiveSession);
    accessor.setProperty(
        keyBuilder.currentState("localhost_3", "session_dead", "testResourceName"),
        stateWithDeadSession);
    runStage(event, new ReadClusterDataStage());
    runStage(event, stage);
    CurrentStateOutput output3 = event.getAttribute(AttributeName.CURRENT_STATE.name());
    String currentState =
        output3.getCurrentState("testResourceName", new Partition("testResourceName_1"),
            "localhost_3");
    AssertJUnit.assertEquals(currentState, "OFFLINE");

  } 
                            #location 58 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              @Test
  public void testSimpleCS() {
    // setup resource
    Map<String, Resource> resourceMap = getResourceMap();

    setupLiveInstances(5);

    event.addAttribute(AttributeName.RESOURCES.name(), resourceMap);
    event.addAttribute(AttributeName.RESOURCES_TO_REBALANCE.name(), resourceMap);
    CurrentStateComputationStage stage = new CurrentStateComputationStage();
    runStage(event, new ReadClusterDataStage());
    runStage(event, stage);
    CurrentStateOutput output1 = event.getAttribute(AttributeName.CURRENT_STATE.name());
    AssertJUnit.assertEquals(
        output1.getCurrentStateMap("testResourceName", new Partition("testResourceName_0")).size(),
        0);

    // Add a state transition messages
    Message message = new Message(Message.MessageType.STATE_TRANSITION, "msg1");
    message.setFromState("OFFLINE");
    message.setToState("SLAVE");
    message.setResourceName("testResourceName");
    message.setPartitionName("testResourceName_1");
    message.setTgtName("localhost_3");
    message.setTgtSessionId("session_3");

    Builder keyBuilder = accessor.keyBuilder();
    accessor.setProperty(keyBuilder.message("localhost_" + 3, message.getId()), message);

    runStage(event, new ReadClusterDataStage());
    runStage(event, stage);
    CurrentStateOutput output2 = event.getAttribute(AttributeName.CURRENT_STATE.name());
    String pendingState =
        output2.getPendingState("testResourceName", new Partition("testResourceName_1"),
            "localhost_3").getToState();
    AssertJUnit.assertEquals(pendingState, "SLAVE");

    ZNRecord record1 = new ZNRecord("testResourceName");
    // Add a current state that matches sessionId and one that does not match
    CurrentState stateWithLiveSession = new CurrentState(record1);
    stateWithLiveSession.setSessionId("session_3");
    stateWithLiveSession.setStateModelDefRef("MasterSlave");
    stateWithLiveSession.setState("testResourceName_1", "OFFLINE");
    ZNRecord record2 = new ZNRecord("testResourceName");
    CurrentState stateWithDeadSession = new CurrentState(record2);
    stateWithDeadSession.setSessionId("session_dead");
    stateWithDeadSession.setStateModelDefRef("MasterSlave");
    stateWithDeadSession.setState("testResourceName_1", "MASTER");

    accessor.setProperty(keyBuilder.currentState("localhost_3", "session_3", "testResourceName"),
        stateWithLiveSession);
    accessor.setProperty(
        keyBuilder.currentState("localhost_3", "session_dead", "testResourceName"),
        stateWithDeadSession);
    runStage(event, new ReadClusterDataStage());
    runStage(event, stage);
    CurrentStateOutput output3 = event.getAttribute(AttributeName.CURRENT_STATE.name());
    String currentState =
        output3.getCurrentState("testResourceName", new Partition("testResourceName_1"),
            "localhost_3");
    AssertJUnit.assertEquals(currentState, "OFFLINE");

  }