Java: Mock testing probably with Mockito

Question

I think I'm not using verify correctly. Here is the test:

@Mock GameMaster mockGM;    
Player pWithMock;

@Before
public void setUpPlayer() throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
 pWithMock = new Player(mockGM);
}

@Test
    public void mockDump() {
     pWithMock.testDump();
     verify(mockGM).emitRandom(); // fails
    }

Here is the code it calls:

public boolean testDump() {
 Letter t = tiles.getRandomTile();
 return dump(t);
}

private boolean dump(Letter tile) {
            if (! gm.canTakeDump() || tiles.count() == 0) {
  return false;
 }

 tiles.remove(tile);
 gm.takeTile(tile);
 for (int i = 0; i < 3; i++) {
  tiles.addTile(gm.emitRandom()); // this is the call I want to verify
 }
 return true;
}

Failure trace:

Wanted but not invoked:
gameMaster.emitRandom();
-> at nth.bananas.test.PlayerTest.mockDump(PlayerTest.java:66)

However, there were other interactions with this mock:
-> at nth.bananas.Player.dump(Player.java:45)

    at nth.bananas.test.PlayerTest.mockDump(PlayerTest.java:66)

The call I want to verify is several layers down. Is there a different way to check this?

Answer 1

I'm not sure to understand what you are doing. Given the following Player class:

public class Player {
    private final GameMaster gm;

    public Player(GameMaster gameMaster) {
        this.gm = gameMaster;
    }

    public void foo() {
        gm.bar(); // this is the call we want to verify
    }
}

And the following GameMaster class:

public class GameMaster {
    public GameMaster() {
    }

    public void bar() {
    }
}

I'd write the test of Player like this:

import static org.mockito.Mockito.verify;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.runners.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)
public class PlayerTest {

    @Mock
    private GameMaster gm;

    @Test
    public void testFoo() {
        Player player = new Player(gm);
        player.foo();
        verify(gm).bar(); // pass
    }
}

Answer 2

There is an error in your test method: it's missing a necessary expectation for the GameMaster#canTakeDump(). This method needs to return true when called from the tested method (because of its use in that if statement at line 45).