Use Mocked object in JUnit / Mockito test

Question

I have a JUnit test that reads

public class  EventHandlerTest  {

    @Mock
    ThreadPoolExtendedExecutor threadPoolExtendedExecutor;

    private EventHandler handler;
    private Map<Queue<SenderTask>> subBuffers = new HashMap<>();


    @Before
    public void setUp() {
        // PROBLEM: threadPoolExtendedExecutor null!
        handler = new EventHandler(subBuffers, threadPoolExtendedExecutor);
    }


}

When I call new in setUp, I have threadPoolExtendedExecutor=null. I would like to insert some mocked threadPoolExtendedExecutor so, I do not have NullPointer problems when calling its methods (so simple interface mock is enough for me at this moment)

You could do it with ThreadPoolExtendedExecutor threadPoolExtendedExecutor = mock(ThreadPoolExtendedExecutor .class) — Lyubomir Papazov, Dec 14 '18 at 09:49

Lho Ben · Accepted Answer · 2018-12-14T10:06:38.827

You can simply mock it using (in setUp)

threadPoolExtendedExecutor = mock(ThreadPoolExtendedExecutor.class);

@Before
public void setUp() {
    threadPoolExtendedExecutor = mock(ThreadPoolExtendedExecutor.class);
    handler = new EventHandler(subBuffers, threadPoolExtendedExecutor);
}

You can also let MockitoJUnitRunner do it for you : don't forget to inject mocks in your service under test by annotating it with @InjectMocks

@RunWith(MockitoJUnitRunner.class)
public class  EventHandlerTest  {

    @Mock
    ThreadPoolExtendedExecutor threadPoolExtendedExecutor;

Adam Siemion · Answer 2 · 2018-12-14T09:59:31.563

1

If you would like to use the @Mock or @InjectMocks annotations on the test class fields then you need to add @RunWith(MockitoJUnitRunner.class) at the class level.

@RunWith(MockitoJUnitRunner.class)
public class  EventHandlerTest  {

    @Mock
    ThreadPoolExtendedExecutor threadPoolExtendedExecutor;

Another approach is to not use the above annotations and manually create mocks by calling org.mockito.Mockito.mock().

edited Dec 14 '18 at 09:59

answered Dec 14 '18 at 09:54

Adam Siemion

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Also have a look at @InjectMocks which would inject mocked object into your unit test class for you so that you don't have to call constructor explicitly. – Rakesh Dec 14 '18 at 09:57
A couple of other options are [discussed here](https://stackoverflow.com/q/10806345) – Dawood ibn Kareem Dec 14 '18 at 09:58
@Rakesh No that's not really what InjectMocks does. – Dawood ibn Kareem Dec 14 '18 at 09:58

Use Mocked object in JUnit / Mockito test

2 Answers2