Control Group within a Control Group

I've started to work with a complex ownership situation and am looking for guidance.  A control group exists and within that group, there is one employer with mutliple entities and 3 different plans, so a smaller control group within the larger control group.  I believe that this smaller group has to be tested on its own and then within the larger group. Is this accurate?  Thanks for any guidance or reference sites. 

You only need to test them all together as one big group. Under 414(b), members of a controlled group are treated as a single employer for testing purposes. So if A, B, and C are all the same employer, and C, D, and E are all the same employer, then logically all of A, B, C, D and E must be the same employer.