Spring JUnit: How to Mock autowired component in autowired component

Question

I've got a Spring component I'd like to test and this component has an autowired attribute which I need to change for the purpose of unit testing. The problem is, that the class uses the autowired component inside the post-construct method so I'm not able to replace it(i.e. via ReflectionTestUtils) before it's actually used.

How should I do that?

This is the class I want to test:

@Component public final class TestedClass{      @Autowired     private Resource resource;      @PostConstruct     private void init(){         //I need this to return different result         resource.getSomething();     } } 

And this is the base of a test case:

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations= "classpath:applicationContext.xml") public class TestedClassTest{      @Autowired     private TestedClass instance;      @Before     private void setUp(){         //this doesn't work because it's executed after the bean is instantiated         ReflectionTestUtils.setField(instance, "resource", new Resource("something"));     } } 

Is there some way to replace the resource with something else before the postconstruct method is invoked? Like to tell Spring JUnit runner to autowire different instance?

Answer 1

You could use Mockito. I am not sure with PostConstruct specifically, but this generally works:

// Create a mock of Resource to change its behaviour for testing @Mock private Resource resource;  // Testing instance, mocked `resource` should be injected here  @InjectMocks @Resource private TestedClass testedClass;  @Before public void setUp() throws Exception {     // Initialize mocks created above     MockitoAnnotations.initMocks(this);     // Change behaviour of `resource`     when(resource.getSomething()).thenReturn("Foo");    }