Test case for entity manager - junit

Question

Getting a null pointer exception on Mockito.when for the below code line.
when(entityManager.createQuery(any(String.class)).setParameter(any(String.class), any(String.class)).getSingleResult()).thenReturn("2");
Trying to mock entity manager which is declared as
#Mock
private EntityManager entityManager;
Any help to resolve this?
Complete test class
#RunWith(MockitoJUnitRunner.class)
public class ASDAOImplTest {
#InjectMocks
ASDAOImpl asdaoImpl=new ASDAOImpl();
#Mock
private EntityManager entityManager;
#Before
public void setUp()
{
ReflectionTestUtils.setField(asdaoImpl,"capLimit", 1);
}
#Test
#Ignore
public void validateCappingTest()
{
when(entityManager.createQuery(any(String.class)).setParameter(any(String.class), any(String.class)).getSingleResult()).thenReturn("2");
asdaoImpl.validateCapping("2");
}
}

Answer 1

Edit: Ah, spoke to soon. The error is here...
when(entityManager.createQuery(any(String.class)).setParameter(...)
entityManager is a mock. Per default, a mock will return null. So, entityManager.createQuery(...) will return null. Calling setParameter on null is a NPE.
What you need to insert is a query mock...
#Mock
private Query query;
...
// when createQuery is called, return the mocked query object (instead of null)
when(entityManager.createQuery(any(String.class)).thenReturn(query);
// make sure that setParameter returns this query object back (would otherwise also be NPE)
when(query.setParameter(any(String.class), any(String.class)).thenReturn(query);
// And return the desired result from getSingleResult
when(query.getSingleResult()).thenReturn("2");
Old answer:
Hard to say without the complete code, but a guess would be that you are misssing the Mockito initialization (the part that actually creates object for the variables annotated with #Mock). This can be done in at least two ways:
// Run the whole test with the Mockito runner...
#RunWith(MockitoJUnitRunner.class)
public class MyTestClass { ...
or...
// Do the Mockito initialization "manually"
#Before
public void init() {
MockitoAnnotations.initMocks(this);
}
Both ways will lead to Mockito creating all the objects where the variables are annotated with #Mock (it also handles #InjectMocks, etc.).
If this doesn't help, you will have to post more of your test class, otherwise probably noone can help.