Question

I have an AuthenticationManager.authenticate(username,password) method that gets called in someMethod of a SomeService under test. The AuthenticationManager is injected into SomeService:

@Component
public class SomeService {
    @Inject
    private AuthenticationManager authenticationManager;

    public void someMethod() {
        authenticationManager.authenticate(username, password);
        // do more stuff that I want to test
    }
}

Now for the unit test I need the authenticate method to just pretend it worked correctly, in my case do nothing, so I can test if the method itself does the expected work (Authentication is tested elsewhere according to the unit testing principles, however authenticate needs to be called inside that method) So I am thinking, I need SomeService to use a mocked AuthenticationManager that will just return and do nothing else when authenticate() gets called by someMethod().

How do I do that with PowerMock (or EasyMock / Mockito, which are part of PowerMock)?

Answer 1

With Mockito you could just do that with this piece of code (using JUnit) :

@RunWith(MockitoJUnitRunner.class)
class SomeServiceTest {

    @Mock AuthenitcationManager authenticationManager;
    @InjectMocks SomeService testedService;

    @Test public void the_expected_behavior() {
        // given
        // nothing, mock is already injected and won't do anything anyway
        // or maybe set the username

        // when
        testService.someMethod

        // then
        verify(authenticationManager).authenticate(eq("user"), anyString())
    }
}

And voila. If you want to have specific behavior, just use the stubbing syntax; see the documentation there.
Also please note that I used BDD keywords, which is a neat way to work / design your test and code while practicing Test Driven Development.

Hope that helps.