Spring JUnit：如何在autowired组件中模拟autowired组件

Question

我有一个Spring组件我想测试，这个组件有一个autowired属性，为了单元测试的目的，我需要更改它。问题是，这个类在后构造方法中使用autowired组件，所以我不能在它实际使用之前替换它（即通过反射）。

我该怎么做？

@Component
public final class TestedClass{

    @Autowired
    private Resource resource;

    @PostConstruct
    private void init(){
        //I need this to return different result
        resource.getSomething();
    }
}

@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"));
    }
}

在调用postconstruct方法之前，有什么方法可以用其他东西替换资源吗？喜欢告诉Spring JUnit runner autowire不同的实例吗？

Answer 1

你可以用Mockito。我不确定postconstruct具体是什么，但这通常是有效的：

// 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");   
}