SpringBootTest - how to replace one bean in runtime configuration?

I am writing an integration test for Spring Boot application. All goes well as long as I'm using 100% runtime configuration for the test. But when I'm trying to provide just one custom bean for the bean, everything breaks.

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class CombinedControllerIntegrationTest2 {

@TestConfiguration
static class ContextConfiguration {

    @Bean
    @Primary
    public SolrDocumentTypeMapRepository solrDocumentTypeMapRepository() {
        LOG.debug("SolrDocumentTypeMapRepository is being initialized.");

// etc.

code variant above is causing the real, runtime SolrDocumentTypeMapRepository to load. ContextConfiguration in my test class is ignored.

If I try to use @Configuration instead of @TestConfiguration on my inner ContextConfiguration, execution falls to another extreme - it ends with

org.springframework.context.ApplicationContextException: Unable to start EmbeddedWebApplicationContext due to missing EmbeddedServletContainerFactory bean.

Because, apparently, the rest of configuration is not loaded.

If I try to put

@ContextConfiguration(classes = {CombinedControllerIntegrationTest2.ContextConfiguration.class,GatewayApplication.class})

on my main testing class, it fails the same way as in #1 - i.e. my ContextConfiguration is ignored.

Any ideas?

P.S. I know I can use @MockBean (and this even works in other cases), but here, because at some point I have dependency on @PostConsruct methods in the main code, @MockBeans are useless.