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

User · Answer

I created blog post on the topic  It contains also link to Github repository with working example    The trick is using test configuration  where you override original spring bean with fake one  You can use  Primary and  Profile annotations for this trick

User · Answer

Spring Boot 1 4 introduced testing annotation called  MockBean  So now mocking and spying on Spring beans is natively supported by Spring Boot

User · Answer

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

User · Answer

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

User · Answer

You can override bean definitions with mocks with spring-reinject https   github com sgri spring-reinject

User · Answer

Another approach in integration testing is to define a new Configuration class and provide it as your  ContextConfiguration  Into the configuration you will be able to mock your beans and also you must define all types of beans which you are using in test s flow  To provide an example      RunWith SpringRunner class   ContextConfiguration loader   AnnotationConfigContextLoader class  public class MockTest    Configuration  static class ContextConfiguration          you beans here used in test flow   Bean     public MockMvc mockMvc             return MockMvcBuilders standaloneSetup   you can declare your controller beans defines on top                     addFilters   optionally filters    build             Defined a mocked bean   Bean     public MyService myMockedService             return Mockito mock MyService class               Autowired  private MockMvc mockMvc     Autowired  MyService myMockedService     Before  public void setup        mock your methods from MyService bean    when myMockedService myMethod   params     thenReturn   my answer           Test  public void test        test your controller which trigger the method from MyService   MvcResult result   mockMvc perform get CONTROLLER URL   andReturn         do your asserts to verify

[java] Spring JUnit: How to Mock autowired component in autowired component

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