I have developed parts of a spring-boot project (first time I am working with Spring-boot). Now I would like to test them and regarding this problem I would like to develop some junit tests now I found alot of tutorials through out the www that provide me with use this and that library/framework (Mockito, spring-boot-starter-test, ...). My problem is I don't know where to start testing - to test AController I need to access BController and create an instance of CBean to create CBean I first need to create DBean which assumes I have EBean and so on. These Beans are for example a user, a project an instance of a model which the constructor I would like to test needs and so on. Now I can somehow create automatic Mockups (this framework probably does need to know more about the project than I do to do thing automatically - no idea how the theory works in practice).
Anyway - how would you start writing unit-tests for such a project - how to setup my mind to start a well ordered process?