Proper usage of Mockito.verify

Question

I'm new to unit testing and i had a simple question regarding the usage of verify method used in Mockito. here's the class i used for testing.

public class Foo{
int n = 0;
void addFoo(String a){
    if(a == "a")
    add(1);
}

protected void add(int num){
    n =1;
}

public int get(){
    return n;
}

}

And here's my Unit test.

public class FooTest {
@Mock Foo f;

@Test
public void test() {
    MockitoAnnotations.initMocks(this);
    f.addFoo("a");

    //Passes
    Mockito.verify(f).addFoo("a");

    //Fails
    Mockito.verify(f).add(1);
}

}

And i get a

   Wanted but not invoked:
f.add(1);
-> at FooTest.test(FooTest.java:22)

However, there were other interactions with this mock:
-> at FooTest.test(FooTest.java:16)

exception.

How do you verify that add(int num) is called ?

Answer 1

I think you misunderstood the point of verify . In your test, Foo f is a mock object - Foo 's internal implementation is ignored, and only the behavior you recorded on it (using when(f.someMethod().thenXXX ) would happen.

The point of mocking and verifying is to test interactions while ignoring the internal implementation. In this example, you would probably have another class that uses Foo , and you'd want to test whether it invokes the correct methods of the given Foo instance.

Quick example:

Assume you have a class the uses the Foo class you presented in your question:

public class FooUser {
    private Foo f;

    public void setFoo(Foo f) {
        this.f = f;
    }

    public Foo getFoo() {
        return f;
    }

    public void addToFoo(String string) {
        f.add(string);
    }
}

Now, you'd want to test that FooUser#addToFoo(String) indeed invokes the correct add(String) method of Foo :

@RunWith (MockitoJUnitRunner.class)
public class FooUserTest {
    @Mock Foo f;
    FooUser fUser;

    @Before
    public void init() {
        fUser = new FooUser();
        fUser.setFoo(f);
    }

    @Test
    public void test() {
        fUser.addToFoo("a");
        Mockito.verify(f).addFoo("a");
    }