Control Group within a Control Group

[Kac1214]

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. 

[C. B. Zeller]

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.