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!"