Mockito and Dependency Injection

ConstructorExample.java

public class Example {

    private Delegate delegate;

    Example(Delegate delegate) {
        this.delegate = delegate;
    }

    public void doIt() {
        delegate.execute();
    }
}

ExampleTest.java

@RunWith(MockitoJUnitRunner.class)
public class ExampleTest {

    @Mock
    Delegate delegateMock;

    @InjectMocks
    Example example;

    @Test
    public void testDoIt() {
        example.doIt();

        verify(delegateMock).execute();
    }
}

FieldExample.java

@Component("example")
public class Example {

    @Autowired
    private Delegate delegate;

    public void doIt() {
        delegate.execute();
    }
}

SetterExample.java

@Named("example")
public class Example {

    private Delegate delegate;

    @Inject
    void setDelegate(Delegate delegate) {
        this.delegate = delegate;
    }

    public void doIt() {
        delegate.execute();
    }
}

The code in this gist shows how Mockito can be used to simplify the dependency injection when writing unit tests. For details, read the blog post at http://blog.jayway.com/2012/02/25/mockito-and-dependency-injection/ .