Is it possibel to change Laravels behavior in overriding .env files?

The 5.3 docu says:

You may also creating a .env.testing file. This file will override values from the .env

I misunderstood this, i was thinking:

if i have 20 entries in .env, i am able to change only one of them, if i create a new file (e.g. .env.new) and add the only changed key here. but laravel does not really takes all keys from .env and overrides them with all keys of .env.new - laravel does not use the .env, it ignores it completly and takes only the file .env.new.
So after all, in my example here, i only have 1 key in my $_ENV instead of 20.

Is this really the wanted behavior?
If yes: Can i change it in the way, i was thinking it should work?

via Chebli Mohamed