unit test fot MembershipAdapter removed ,added and attributeChanged

Why is a MembershipListener implemented on a MapStoreAdapter. This is very confusing and will not help us in the future to understand what the purpose of the test is. Keep the 'WTF' in code as low as possible.

https://c1.staticflickr.com/3/2203/2245445147_ff54c5997d.jpg