How to override bean with Mock in @SpringBootTest?

Using Spring Boot 2.0.0.M5.

I need to set up an integration test which has the same context as working application but with one bean replaced by a Mockito mock.

Solved the problem easily with org.springframework.boot.test.mock.mockito.MockBean annotated property. The thing I do not like about this solution is that now IDE says this property is never used and I agree with the warning.

How else can I mock one bean in Spring boot application test context? I am more familiar with configuring test context in non-boot spring and @ContextConfiguration annotation, but I can't use it now because spring boot properties and other boot-related stuff stop working. So I want to keep @SpringBootTest and achieve what I want.

In reference documentation I've read that I can use @TestConfiguration:

If you want to customize the primary configuration, you can use a nested @TestConfiguration class. Unlike a nested @Configuration class, which would be used instead of your application’s primary configuration, a nested @TestConfiguration class is used in addition to your application’s primary configuration.

Tried the following code

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(initializers = FetchIntegrationTest.Initializer.class, classes = Server.class)
@Configuration
public class FetchIntegrationTest extends TestContainersAbstractTest {

    @TestConfiguration
    public static class NestedConfig {
        @Bean
        @Primary
        public ScheduledSettingsFetcher scheduledSettingsFetcher() {
            return Mockito.mock(ScheduledSettingsFetcher.class);
        }
    }
        ....

    public static class Initializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
        @Override
        public void initialize(@NonNull ConfigurableApplicationContext configurableApplicationContext) {
            ConfigurableEnvironment env = configurableApplicationContext.getEnvironment();
            TestPropertyValues.of("someservice.address=" + testcontainersService.getContainerIpAddress()).applyTo(env);
        }
    }
}

but unfortunately, it did not work out. I still have my original ScheduledSettingsFetcher instantiated instead of declared mock.