Laravel 5.1 not using correct .env values

I'm using Laravel 5.1.44, and even though I have both a .env.testing file setup with different values, as well as App::environment() returning 'testing', Laravel still seems to only be using values from the main .env file.

Is there something else I should be double-checking to make sure I didn't screw up or forget to set something?

via Chebli Mohamed