In what kind of environments do the Agile testing methodologies prove very successful and where do they dont?
The agile methods of testing can be a very good way of developing a project which has to have a periodic deliverable and which has a very few members in the team with fixed resources. In such scenarios, the Agile methods can help to get the maximum efficiency and stability in the products under development. In such cases the requirements are not so varied and remain quite constant.
On the other hand, if we consider a very large organization which is developing a software or any other product which has lot of modules and lot of functional requirements (business logics) then agile methods may just prove to be a hurdle in the development of different modules. So it is not a good idea to adopt agile testing methods in large projects with a wider scope of operations.