Not sure what you mean here. If ```namespace_and_class[0]``` is actually set to ```Katello```, then ```Object.qualified_const_get("Katello::FiltersHelper")``` will either return the const, or throw ```NameError: uninitialized constant``` exception. 

There's a test that verifies this behaviour: ```test_engine_search_path_is_used_when_engine_override_available```.