How to use @ComponentScan together with test-specific ContextConfigurations in SpringJunit4TestRunner?
<p>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.</p>

<p>Here is a sketch of the setup:</p>

<p>src/main/java:</p>

<pre><code>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...
}
</code></pre>

<p>src/test/java:</p>

<pre><code>package com.example.myapp;

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

    @Autowired
    Component1 component1; // &lt;-- 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; // &lt;-- 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...
    }
}
</code></pre>

<p>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.</p>

<p>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).</p>

<p>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?</p>