If you’re using PHPUnit for running not only unit but UI tests too, you might want to be able to run them against different browsers. There are several ways of doing that, some of which involve hardcoding some stuff in your phpunit.xml or having multiple phpunit.xx.yml files or, worse, hardcoding it in the tests themselves.
Let’s say you have a UserManager class that controls the application rules pertaining to the User class. One of those rules is to encode a user’s password if her plain password is set. Here’s a test that would test that: