I find the following confusing and potentially cause of error:
- we will register paths for libraries in the order we want to lookup
- we will get a FQDN of the controller that we need from the route function
- we will instantiate that controller afterwards
BUT
the controller instantiated will be defined based on the include_path and not the paths registrations.

Would that make sense to have the set_include_path inside the paths registration?

typo "Identifiers"

shouldn't this better be protected?

define "$controller = '';" before the foreach for in case there is no path at all.

Or "return '';" in the end of the function and "return $controller;" instead of the "break;"

$this->paths[$id] is potentially not set

maybe add a third paths in here, just to test that the lookup stops as soon as it finds a controller

I think we should have an extra failure test in case no path is defined at all.

I think it is confusing to use foo/bar everywhere
the first 'foo/bar' is meant for 'controller/method' while the second one is a folder path

That makes the tests difficult to read

2016 :D

and in the unit tests if we care

Ship It!