I have created a simple unit test but IntelliJ is incorrectly highlighting it red. marking it as an error
No beans?
I had similar issue in Spring Boot application. The application utilizes Feign (HTTP client synthetizing requests from annotated interfaces). Having interface SomeClient annotated with @FeignClient, Feign generates runtime proxy class implementing this interface. When some Spring component tries to autowire bean of type SomeClient, Idea complains no bean of type SomeClient found since no real class actually exists in project and Idea is not taught to understand @FeignClient annotation in any way.
Solution: annotate interface SomeClient with @Component. (In our case, we don't use @FeignClient annotation on SomeClient directly, we rather use metaannotation @OurProjectFeignClient which is annotated @FeignClient and adding @Component annotation to it works as well.)