Mockito doNothing doesn't work when a Method called with void method call inside

Question

Main Class

public class BootSample {

    public int call(int m) {
        System.out.println("Entering into Call Method");
        int n = m*10;
        TestUtil testUtil = new TestUtil();
        testUtil.add(m, n);
        System.out.println("End of Call Method Value n : " + n);
        return n;
    }

}

Util Class

public class TestUtil {

    public void add(int a, int b) {
        System.out.println(" Entering into TestUtil Method ");
        int c = a +b;
        System.out.println(" End of TestUtil Method Value : " + c);
    }

}

Test Class

@RunWith(MockitoJUnitRunner.class)
public class BootSampleTest {

    @Mock
    TestUtil testUtil; 

    @Before
    public void setup() {

    }

    @Test
    public void utilSuccess() throws Exception {
        BootSample bootSample = new BootSample();
        doNothing().when(testUtil).add(any(Integer.class),any(Integer.class));
        int result = bootSample.call(10); 
        assertEquals(result,100);
    }

}

Output :

Entering into Call Method
 Entering into TestUtil Method 
 End of TestUtil Method Value : 110
End of Call Method Value n : 100

I'm trying to mock util void method call with doNothing but doesn't work.Can anyone please help me with solution? I'm stuck with similar functionality in our application.

1. This Test will always fail. 2. You need to mock your class — logger, Jan 10 '18 at 22:32

score 2 · Accepted Answer · answered Jan 10 '18 at 22:33

2

The problem is that your call method is responsible for creating a TestUtil object, and that object can't be mocked. Try adding TestUtil as a constructor argument like so:

public class BootSample {

    private TestUtil testUtil;

    public BootSample(TestUtil testUtil) {
        this.testUtil = testUtil;
    }

    public int call(int m) {
        System.out.println("Entering into Call Method");
        int n = m*10;
        testUtil.add(m, n);
        System.out.println("End of Call Method Value n : " + n);
        return n;
    }
}

You then need to mock the TestUtil class and pass the mock to the BootSample class:

BootSample bootSample = new BootSample(testUtil);

answered Jan 10 '18 at 22:33

Eric

2,008
3
18
31

public class BootSample { public BootSample(Object mac) { this.mac = mac; } public int call(int m) { System.out.println("Entering into Call Method"); int n = m*10; TestUtil testUtil = new TestUtil(); testUtil.add(m, n); System.out.println("End of Call Method Value n : " + n); return n; } } Caller BootSample bootSample = new BootSample(macObject); bootSample.call(15); – chebs Jan 11 '18 at 21:12
Thank You @Eric .This works but I have another main constructor which accepts some value where i cannot create new constructor of BootSample with testUtil. Is there any alternative approach ? like above – chebs Jan 11 '18 at 21:12
If you can't add the `TestUtil` object to a new constructor or an existing constructor, then you could just set the `TestUtil` object using a setter and calling it. Somehow you're going to have to inject the mock, whether it is through a constructor or a setter. – Eric Jan 11 '18 at 22:41
Thank You very much.Can you explain little more on using setter that would be great help.Really appreciate your help.Thanks a ton. – chebs Jan 12 '18 at 19:27

score 1 · Answer 2 · answered Jan 10 '18 at 22:33

1

If you're seeing the System.out.printlns from your TestUtil class then it isn't mocked. It looks like you're missing the @InjectMocks on BootSample to tell Mockito to inject your mocked TestUtil into it.

See the example in the docs here: http://static.javadoc.io/org.mockito/mockito-core/2.13.0/org/mockito/InjectMocks.html

answered Jan 10 '18 at 22:33

Kevin Hooke

2,583
2
19
33

2

If you use `@InjectMocks`, the `TestUtil` needs to be injected in your production as well, of course. – Johannes Jasper Jan 10 '18 at 22:37
The `@InjectMocks` approach has the disadvantage that you can declare more mocks but "forget" to add them to the constructor parameters. Your test does not get a compile error. And by the rules of *TDD* you are not allowed to change the production code then... – Timothy Truckle Jan 10 '18 at 22:51
1

Thank You Kevin for your input it was really helpful. – chebs Jan 17 '18 at 16:25

score 1 · Answer 3 · edited Jan 11 '18 at 09:06

1

You can use Mockito.anyInt() instead of Integer.class, code example :

Mockito.doNothing().when(testUtil).add(Mockito.anyInt(),Mockito.anyInt());

edited Jan 11 '18 at 09:06

Stefan Birkner

24,059
12
57
72

answered Jan 10 '18 at 23:25

Utkarsh Kumar

76
8

Mockito doNothing doesn't work when a Method called with void method call inside

3 Answers3

Linked