The scope is a (depth|level) of a hierarchical namespace.
The global scope is the root of the namespace.
- the root directory for a file system
- the root catalog for a database system
- In a file system, in a specific directory, you can't have two file with the same name.
- In a table, you can't have two rows with the same primary key.
As with each group functionality, the less you have in your scope, the beter.
You should follow the magical number (seven +-2)
The code quality / maintainability will increase, your test will be more isolated