I assume that the Entry Point uses the Container to obtain an instance of service A, passing it to whomever needs it. I also assume that the Entry Point similarly controls the lifecycle of service B. In both cases, a smoke test would help check that the Entry Point assembles the application correctly. Of course, we add the fewest smoke tests possible.
When you register service A in a Container, you must do this because you want some Framework (that uses the Container) to instantiate a class X for you, and X uses A. Can you write a smoke test for the application that discovers all the classes (like X) that Framework will instantiate for you, and simply try instantiating them all, checking for exceptions? That might help. If not, then why not?
I'd like to avoid testing the plumbing in the style of "I added service X, not let me verify that the container can instantiate an X with the expected implementation". I'd rather test that the system can instantiate the things that need X.