Overriding an Autowired Bean in Unit Tests

Question

Is there a simple way I can easily override an autowired bean in specific unit tests? There is only a single bean of every type in the compile classes so it's not a problem for autowiring in this case. The test classes would contain additional mocks. When running a unit test I'd simply like to specify an additional Configuration that says basically, while running this unit test use this mock instead of the standard bean.

Profiles seem a bit overkill for what I require and I'm not sure this would be achievable with the Primary annotation as different unit test could have different mocks.

Answer 1

If you just simply want to provide a different bean in your tests, i think you don't need to use spring profiles or mockito.

Just do the following:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = { TestConfig.class })
public class MyTest
{
    @Configuration
    @Import(Application.class) // the actual configuration
    public static class TestConfig
    {
        @Bean
        public IMyService myService()
        {
            return new MockedMyService();
        }
    }

    @Test
    public void test()
    {
        ....
    }
}

NOTE: tested with spring boot 1.3.2 / spring 4.2.4

Answer 2

In Spring Boot 1.4 there's a simple way for doing that:

@RunWith(SpringRunner.class)
@SpringBootTest(classes = { MyApplication.class })
public class MyTests {
    @MockBean
    private MyBeanClass myTestBean;

    @Before
    public void setup() {
         ...
         when(myTestBean.doSomething()).thenReturn(someResult);
    }

    @Test
    public void test() {
         // MyBeanClass bean is replaced with myTestBean in the ApplicationContext here
    }
}

Answer 3

I had similar problem and I solved with a mix and I find this one more useful and reusable. I created a spring profile for the tests and a config class that overrides the beans I want to mock in a very simple way:

@Profile("test")
@Configuration
@Import(ApplicationConfiguration.class)
public class ConfigurationTests {

    @MockBean
    private Producer kafkaProducer;

    @MockBean
    private SlackNotifier slackNotifier;

}

By doing that I can @Autowire those mock beans and use mockito to verify on them. Main advantage is that now all tests seamlessly get the mock beans without any per-test change. Tested with:

spring boot 1.4.2