PHPUnit: dynamically loading different env files

I'm working on a project (Laravel 6) with multiple developers.

We run PHPUnit regularly when developing, and we have the .env.testing and phpunit.xml files committed to the repo so that all developers have the same testing environment defined.

We are now looking at how we could run PHPUnit on our development server as a final check. However, because the .env.testing and phpunit.xml files are geared to run on our local machines, how can I tell PHPUnit on the development server to use a separate .env file?