Question

Say I have the following code:

public class ClassToTest
{
    AnotherClass anotherClass;

    public void methodToTest( int x, int y )
    {
        int z = x + y
        anotherClass.receiveSomething( z );
    }
}

public class AnotherClass
{
    public void receiveSomething( int z ) {.. do something.. }  
}

I want to make assertion on the value of the variable z. How do I do this without refactoring? Variables x, y, and z could be some other Java class types, and I just used “int” for simplicity.

Answer 1

You can write the following. Of course dependency injection and test method might change depending on your current implementation and/or your test scenarios.

@RunWith(MockitoJUnitRunner.class)
public class ClassToTestTest {

    @Mock AnotherClass anotherClass;
    @InjectMocks ClassToTest classToTest;

    @Test public void ensure_that_value___Z___is_passed_to___AnotherClass() {
        classToTest.methodToTest(1, 2);

        verify(anotherClass).receiveSomething(eq(3));
    }
}

Written with Mockito 1.9.5-rc1 in mind.

Also instead of using the eq matcher you can instead use an ArgumentCaptor, which will capture values or value references (in case of objects). You’ll be able to perform additional assertions on the captured value(s). For example using Truth or FEST-Assert.

This could look like :

@RunWith(MockitoJUnitRunner.class)
public class ClassToTestTest {

    ...
    @Captor ArgumentCaptor<List<Z>> listCaptor

    @Test public void ensure_that_list_with_value___Z___is_passed_to___AnotherClass() {
        // given

        // when
        ...

        // then
        verify(anotherClass).receiveList(listCaptor.capture());
        assertThat(listCaptor.getValue()).contains(Z);
    }
}

Cheers,