I'm trying to write JUnit tests for a stateless session bean that has an injected EntityManager:
@Stateless
public class MyServiceBean implements MyService, ... {
@PersistenceContext
private EntityManager em;
....
Of course, without doing anything, em remains null in the flow of the test...
The tests should run standalone (NOT in a Java EE container).
How do I do that please? (simple solutions will be most appreciated :-)
Simple answer is don't do that, if you want to have persistence context injected like in the real working application, use embedded/external server for testing. More info about testing EJBs and JPA you can find here: Best current framework for unit testing EJB3 / JPA
You mock it with Mockito. You add dependency of Mockito and with @MockitoJUnitRunner annotation on your class, you can @Mock EntityManger entityManager and @InjectMocks MyService service in your unit test. You will stub it like when(entityManager.findById(id)).thenReturn(somethingIWantItToReturn);.
If you want to test your data access logic (criteria code, jpql queries, etc) what I'd do is using HSQLDB. There is no need to mock the EntityManager or have a Java EE container and it integrates nicely with the build process.
