Mockito mocking a method calls the actual method

Question

I am trying to mock method createInstanceB() using Mockito.when() as well as doReturn(). This always calls real method.

For example:

Class A {
  public B createInstanceB(any, any) {
    B b = new B();
    b.api();
  }
}

I am using the code below

import org.mockito.Mockito;
import static org.mockito.Mockito.*;

    Class ATest {
      A a;
      B b;

      @Before
      Public void setup{
        a = A.getInstance();
        b = mock(B.class);
      }
  
      @Test
      public void testCreateInstanceB(){
        Mockito.when(a.createInstanceB(any(),any()).thenReturn(b);
        ...
      }
    }

I tried doReturn(mock) as well.

Answer 1

As StvnBrkdll recommended, use a Spy if you're needing to use an actual instance. But that can still call the real method sometimes if using Mockito.when() as you are in your example. As an alternative, look at Mockito.doReturn(). For example using your code: Mockito.doReturn(b).when(a).createInstanceB(any(),any()); This will now only return b and never call the actual method of createInstanceB.

Btw, their docs have a section about this. See the part under "Important gotcha on spying real objects!"

Answer 2

The problem with the code is that it is calling Mockito.when() on an actual instance of A, not a mock. Mockito.when() only works with mock objects, not the real thing.

If you need to have methods "mocked" (stubbed) on "real" objects, consider using Mockito.spy(). For more information on using "spies", see this post.

Something like this will be close to what you want:

Class ATest{
A a ;
A aSpy;
B b;

@Before
Public void setup{
  a= A.getInstance();
  aSpy = Mockito.spy(a);
  b= mock(B.class);
}

@Test
public void testCreateInstanceB(){
 Mockito.when(aSpy.createInstanceB(any(),any()).thenreturn(b);
 ...
}

You will need to use aSpy, not a in your test code.

Answer 3

I faced this problem. Both of these methods thenReturn() and doReturn() seem to do the same in my case: that is they are calling the actual method. Using stub worked for me:

PowerMockito.stub(PowerMockito.method(A.class, "createInstance", argtypes)).toReturn(b);

Make sure you mock the constructor of A as well as using PowerMockito.whenNew() if you create a new object and add A.class to @PrepareForTest.

Answer 4

As per @StvnBrkdll's answer, in my case the problem was that I was using the @Autowired annotation instead of @MockBean for the method I was trying to mock, and that was causing the real implementation to be called.