Return different values from mock, depending on args

Question

I'm trying to make mock that should return different value if the argument had concrete class. I created tableVerificationService mock object and created these when conditions.

Mockito.when(tableVerificationService.verify(Mockito.any())).thenReturn(true);
Mockito.when(tableVerificationService.verify(Mockito.any(DTable.class))).thenReturn(false);

But now it returns false in any case, even if i pass another from DTable object.

If i change order of these two lines, it will return true in all cases. Is there any way to make correct behavior?

Which version of Mockito are you using? Mockito 1.x would have the behavior you describe and would require `isA`, but Mockito 2.0+ this should work as you have it. See: [What's the difference between Mockito Matchers isA, any, eq, and same?](https://stackoverflow.com/q/30890011/1426891) — Jeff Bowman, Oct 29 '21 at 20:19

score 2 · Accepted Answer · answered Oct 30 '21 at 09:47

You can use .thenAnswer() or .then() (shorter) to have more control of the returned value.

An example might visualize this better.

Let's assume we want to mock the Java class:

public class OtherService {

  public String doStuff(String a) {
    return a;
  }
}

... and we want to return "even" if the passed String is even and "uneven" otherwise.

By using .then() we get access to the InvocationOnMock and can access the passed argument. This helps to determine the returned value:

class MockitoExampleTest {

  @Test
  void testMe() {

    OtherService otherService = Mockito.mock(OtherService.class);

    when(otherService.doStuff(ArgumentMatchers.anyString())).then(invocationOnMock -> {
      String passedString = invocationOnMock.getArgument(0);

      if (passedString.length() % 2 == 0) {
        return "even";
      } else {
        return "uneven";
      }
    });

    System.out.println(otherService.doStuff("duke")); // even
    System.out.println(otherService.doStuff("egg")); // uneven

  }
}

With this technique you can check the passed argument and determine if it's your concrete class and then return whatever value you want.

Yes, thanks, that is very useful and flexible approach. But in my case Mockito.isA was enough to determine the class of the argument. — Ruslan, Oct 30 '21 at 10:07

Return different values from mock, depending on args

1 Answers1