Apache Storm Junit test case for bolt

Question

I have written a bolt and a topology. Now I need to do a Junit test case. My actual input is a Json and in my bolt I have written code to store this in MySQL. Now I need to test my logic which I have written in execute() method. So how to create a object for the tuple in the test case or is there any other way to do this. I have attached the code of my execute() method.

public void execute(Tuple input, BasicOutputCollector collector) {
    int size = input.getFields().size();
    Fields fields = input.getFields();
    if (size == 1) {
        logger.info("PostbackToRDSBolt execute method starts");
        try {
                eventJson = (JSONObject) JSONSerializer.toJSON((String) input.getValueByField(fields.get(0)));
                address = (String) input.getValueByField(fields.get(0));
                Id = (String) eventJson.get("Id");
                click = (String) eventJson.get("click");
                time = (String) eventJson.get("time");
                uuid = UUID.randomUUID().toString();
                type = "post";
                //Class.forName("com.mysql.jdbc.Driver");
                con = DriverManager.getConnection(
                        dBUrl, username,
                        password);
                stmt = con.createStatement();
                stmt.execute("INSERT INTO " + tableName
                        + "(id,data,type,txnid,groupname,time)values('" + uuid
                        + "','" + address + "'," + "'" + type + "','"
                        + Id + "','" + click + "','" + time
                        + "')");
                logger.info("inserted successfully in mysql");
            } catch (SQLException e) {
                e.printStackTrace();
            } catch (Exception e1) {
                logger.info("" + e1);
                e1.printStackTrace();
            }
        }
    }
}

Answer 1

If you want to do JUnit testing, one approach would be to use Mockito library:

For example:

@Test
public void testExecute() {
    Tuple t = mock(Tuple.class);
    when(t.getFields()).thenReturn(new Fields("myAttribute"));
    when(t.getValueByField("myAttribute").thenReturn("my json string to be tested");

    MyBolt b = new MyBolt();
    b.execute(t, mock(BasicOutputCollector.class));

    // put your assertions here
}

For this to work, you should change your code in execute() a little bit. From

int size = input.getFields().size();
Fields fields = input.getFields();

to

Fields fields = input.getFields();
int size = fields.size();

Otherwise, input.getFields() is called twice but the test only specified a single return value for this method, and thus, the second call will return null. (As an alternative, you can also mock both calls to getFields().)

If you don't want to mock everything you can also instantiate TupleImpl objects (Tuple t = new TupleImpl(...)) and pass them to execute() in your test.