If you are testing a logic class and it is calling some internal void methods the doNothing is perfect.
A very simple example is that if you have a UserService
that has @Autowired
jpa resposiroty UserRepository
...
class UserService{
@Autowired
UserRepository userRepository;
...
}
then in the test class for UserService
you will do
...
class TestUserService{
@Mock
UserRepository userRepository;
@InjectMocks
UserService userService;
...
}
@InjectMocks
tells the framework that take the @Mock UserRepository userRespository;
and inject that into userService
so rather than auto wiring a real instance of UserRepository
a Mock of UserRepository
will be injected in userService
.
It depends on the kind of test double you want to interact with:
In other words, with mocking the only useful interactions with a collaborator are the ones that you provide. By default functions will return null, void methods do nothing.
To add a bit to accepted answer ...
If you get an UnfinishedStubbingException
, be sure to set the method to be stubbed after the when
closure, which is different than when you write Mockito.when
Mockito.doNothing().when(mock).method() //method is declared after 'when' closes
Mockito.when(mock.method()).thenReturn(something) //method is declared inside 'when'
doThrow : Basically used when you want to throw an exception when a method is being called within a mock object.
public void validateEntity(final Object object){}
Mockito.doThrow(IllegalArgumentException.class)
.when(validationService).validateEntity(Matchers.any(AnyObjectClass.class));
doReturn : Used when you want to send back a return value when a method is executed.
public Socket getCosmosSocket() throws IOException {}
Mockito.doReturn(cosmosSocket).when(cosmosServiceImpl).getCosmosSocket();
doAnswer: Sometimes you need to do some actions with the arguments that are passed to the method, for example, add some values, make some calculations or even modify them doAnswer gives you the Answer interface that being executed in the moment that method is called, this interface allows you to interact with the parameters via the InvocationOnMock argument. Also, the return value of answer method will be the return value of the mocked method.
public ReturnValueObject quickChange(Object1 object);
Mockito.doAnswer(new Answer<ReturnValueObject>() {
@Override
public ReturnValueObject answer(final InvocationOnMock invocation) throws Throwable {
final Object1 originalArgument = (invocation.getArguments())[0];
final ReturnValueObject returnedValue = new ReturnValueObject();
returnedValue.setCost(new Cost());
return returnedValue ;
}
}).when(priceChangeRequestService).quickCharge(Matchers.any(Object1.class));
doNothing: Is the easiest of the list, basically it tells Mockito to do nothing when a method in a mock object is called. Sometimes used in void return methods or method that does not have side effects, or are not related to the unit testing you are doing.
public void updateRequestActionAndApproval(final List<Object1> cmItems);
Mockito.doNothing().when(pagLogService).updateRequestActionAndApproval(
Matchers.any(Object1.class));
Source: Stackoverflow.com