A clean way to do this is to just bake the possibility to switch to the special testing settings into your code.
One possibility would be to add one (or a few) optional arguments that can override the ‘default’ settings that are used.
The advantage on this over relying on Application.get_env/put_env is that it is completely separate between test-cases (it is ‘functionally pure’). This helps reasoning about the tests, but also e.g. allows your tests to run concurrently.
