How do I make a JMS ObjectMessage for a Unit Test? - junit

Question

I'm trying to write a unit test for an MDB. The goal of my test is to make sure that the logic in the MDB can identify the correct type of object in the ObjectMessage and process it. However, I can't figure out how to make an ObjectMessage so I can test it. I keep getting null pointer exceptions.
Here is my unit test:
/**
* Test of the logic in the MDB
*/
#RunWith(JMockit.class)
#ExtendWith(TimingExtension.class)
class MDBTest
{
protected MyMDB mdb;
#BeforeEach
public void setup() throws NamingException, CreateHeaderException, DatatypeConfigurationException, PropertiesDataException
{
mdb = new MyMDB();
}
/**
* Test the processing of the messages by the MDB
*/
#Test
void testReceivingMessage() throws JMSException, IOException
{
MyFirstObject testMsg = getTestMessage();
ObjectMessage msg = null;
Session session = null;
new MockUp<ObjectMessage>()
{
#Mock
public void $init()
{
}
#Mock
public Serializable getObject()
{
return testMsg;
}
};
new MockUp<Session>()
{
#Mock
public void $init()
{
}
#Mock
public ObjectMessage createObjectMessage(Serializable object)
{
return msg;
}
};
// !!!! Null pointer here on Session !!!!
ObjectMessage msgToSend = session.createObjectMessage(testMsg);
mdb.onMessage(msgToSend);
assertEquals(1, mdb.getNumMyFirstObjectMsgs());
}
/**
* Create a Test Message
*
* #return the test message
* #throws IOException
*/
protected MyFirstObject getTestMessage) throws IOException
{
MyFirstObject myObj = new MyFirstObject();
myObj.id = 0123;
myObj.description = "TestMessage";
return myObj;
}
}
I feel like I should be able to initialize Session somehow, but I need to do it without using an additional library like Mockrunner.
Any suggestions?

Answer 1

I would try to address this in a different style. Provide a mock client, that will just mock the right API.
We should mock only a set of functions required for message retrieval and processing but that means we might have to provide a custom implementation for some of the APIs available in the EJB/JMS library. The mock client will have a function to push messages on a given topic/queue/channel, message can be simple String.
A simple implementation might look like this, in this other methods have been omitted for simplicity.
// JMSClientImpl is an implementation of Connection interface.
public class MyJmsTestClient extends JMSClientImpl{
Map<String, String> channelToMessage = new ConcurrentHashMap<>();
public Map<String, String> getMessageMap(){
return channelToMessage;
}
public void enqueMessage(String channel, String message){
channelToMessage.put(channe, message);
}
#Override
public Session createSession(){
return new MyTestSession(this);
}
}
// A class that implements some of the methods from session interface
public MyTestSession extends SessionImpl{
private MyJmsTestClient jmsClient;
MyTestSession(MyJmsTestClient jmsClient){
this.jmsClient = jmsClient;
}
// override methods that fetches messages from remote JMS
// Here you can just return messages from MyJmsTestClient
// override other necessary methods like ack/nack etc
MessageConsumer createConsumer(Destination destination) throws JMSException{
// returns a test consume
}
}
A class that implements methods from MessageConsumer interface
class TestMessageConsumer extends MessageConsumerImpl {
private MyJmsTestClient jmsClient;
private Destination destination;
TestMessageConsumer(MyJmsTestClient jmsClient, Destination destination){
this.jmsClient = jmsClient;
this.destination = destination;
}
Message receive() throws JMSException{
//return message from client
}
}
There's no straight forward, you can see if there're any library that can provide you embedded JMS client feature.