I wrote my own @RestControllerAdvice bean and wanted it to be reusable through my projects.
Thus, I wrote my own @AutoConfiguration to set it up, which works like a charm - except for @WebMvcTests where it is not autoconfigured.
I understand that @WebMvcTest does not autoconfigure everything but now I wonder how to set it up properly (without @Autowiring it in every MvcTest).
Found this related question that showed me the way.
You can add autoconfigurations that should be eligible for WebMvcTest bei using spring factories. For instance, see the spring-boot-test-autoconfigure repo.
In my case, add a file org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureWebMvc.imports
named to src/main/resources/META-INF/spring
and add my autoconfiguration.