How to use @ComponentScan together with test-specific ContextConfigurations in SpringJunit4TestRunner?

Question

I am testing a Spring Boot application. I have several test classes, each of which needs a different set of mocked or otherwise customized beans.

Here is a sketch of the setup:

src/main/java:

package com.example.myapp;

@SpringBootApplication
@ComponentScan(
        basePackageClasses = {
                MyApplication.class,
                ImportantConfigurationFromSomeLibrary.class,
                ImportantConfigurationFromAnotherLibrary.class})
@EnableFeignClients
@EnableHystrix
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

package com.example.myapp.feature1;

@Component
public class Component1 {
    @Autowired
    ServiceClient serviceClient;

    @Autowired
    SpringDataJpaRepository dbRepository;

    @Autowired
    ThingFromSomeLibrary importantThingIDontWantToExplicitlyConstructInTests;

    // methods I want to test...
}

src/test/java:

package com.example.myapp;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = MyApplication.class)
@WebAppConfiguration
@ActiveProfiles("test")
public class Component1TestWithFakeCommunication {

    @Autowired
    Component1 component1; // <-- the thing we're testing. wants the above mock implementations of beans wired into it.

    @Autowired
    ServiceClient mockedServiceClient;

    @Configuration
    static class ContextConfiguration {
        @Bean
        @Primary
        public ServiceClient mockedServiceClient() {
            return mock(ServiceClient.class);
        }
    }

    @Before
    public void setup() {
        reset(mockedServiceClient);
    }

    @Test
    public void shouldBehaveACertainWay() {
        // customize mock, call component methods, assert results...
    }
}

package com.example.myapp;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = MyApplication.class)
@WebAppConfiguration
@ActiveProfiles("test")
public class Component1TestWithRealCommunication {

    @Autowired
    Component1 component1; // <-- the thing we're testing. wants the real implementations in this test.

    @Autowired
    ServiceClient mockedServiceClient;

    @Before
    public void setup() {
        reset(mockedServiceClient);
    }

    @Test
    public void shouldBehaveACertainWay() {
        // call component methods, assert results...
    }
}

The problem with the above setup is that the component scan configured in MyApplication picks up Component1TestWithFakeCommunication.ContextConfiguration, so I get a mock ServiceClient even in Component1TestWithRealCommunication where I want the real ServiceClient implementation.

Although I could use @Autowired constructors and build up the components myself in both tests, there is a sufficient amount of stuff with complicated setup that I would rather have Spring TestContext set up for me (for example, Spring Data JPA repositories, components from libraries outside the app that pull beans from the Spring context, etc.). Nesting a Spring configuration inside the test that can locally override certain bean definitions within the Spring context feels like it should be a clean way to do this; the only downfall is that these nested configurations end up affecting all Spring TestContext tests that base their configuration on MyApplication (which component scans the app package).

How do I modify my setup so I still get a "mostly real" Spring context for my tests with just a few locally overridden beans in each test class?

Answer 1

The following should help you to achieve your goal by introducing a new fake-communication profile that is applicable only to the current test class.

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = MyApplication.class)
@WebAppConfiguration
@ActiveProfiles({"test", "fake-communication"})
public class Component1TestWithFakeCommunication {

    // @Autowired ...

    @Profile("fake-communication")
    @Configuration
    static class ContextConfiguration {
        @Bean
        @Primary
        public ServiceClient mockedServiceClient() {
            return mock(ServiceClient.class);
        }
    }
}

Answer 2

If you have a @SpringBootTest you can just annotate the service you want to mock with @MockBean. As simple as that.

Answer 3

You may use additional explicit profiles to avoid such test configurations to be picked up (as suggested in another answer). I also did it and even created some library support for that.

However, Spring-Boot is clever and it has a built-in "type filter" to resolve this issue automatically. For this to work, you need to remove your @ComponentScan annotation, which would find your test configurations, and let the @SpringBootApplication do the work. In your example, just remove this:

@SpringBootApplication
@ComponentScan(
    basePackageClasses = {
            MyApplication.class,
            ImportantConfigurationFromSomeLibrary.class,
            ImportantConfigurationFromAnotherLibrary.class})

and replace it with:

@SpringBootApplication(scanBasePackageClasses= {
            MyApplication.class,
            ImportantConfigurationFromSomeLibrary.class,
            ImportantConfigurationFromAnotherLibrary.class})

You may also need to annotate your test as @SpringBootTest. This should avoid auto-scanning any inner-class configurations (and components) except for those residing in the current test.

Answer 4

I would do a couple of things:

1. Move your test classes into a different package to avoid @ComponentScaning them.
2. In Component1TestWithFakeCommunication, change @SpringApplicationConfiguration(classes = MyApplication.class) to @SpringApplicationConfiguration(classes = {MyApplication.class, Component1TestWithFakeCommunication.ContextConfiguration.class})

That should give Spring sufficient information to mock up the test beans, but it should prevent the runtime ApplicationContext from noticing your test beans as well.