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 can provide a new testContext.xml in which the @Autowired bean you define is of the type you need for your test.