I like actions. In particular, I like how they encourage us to think about the behaviour of our applications. I also like the individual test-files focussed on a single behaviour.

That said, I often feel that simple ones (like this) should just be methods on our models.

i.e.

$user->awardExperience(200);

Then your test is even simpler.

$user = User::factory()->create();

$user->awardExperience(1000);

expect($user->experience)->toBe(1000);

Note: You could still put this in a AwardExperienceTest.php, rather then a UserTest.php

The more complex question then, is when should we reach for actions vs model methods? I'm not sure honestly. I think the more objects being touched, the more likely I am to reach for an action. This is because it becomes harder to discern which model the behaviour really belongs too. Even then I'm a bit hesitant. I think these situations often come up because we're missing a domain model. So I tend to ask, "What model does this behaviour belong too?" and if I can't find a good answer I ask "what model doesn't exist that this behaviour should belong to?"

An anecdote. I once had an InviteEmployeeAction in a payroll app. It sent an email to the employee prompting them to register an account, or just let them know they've been added to the job. It worked fine, but something bothered me. Eventually, I introduced a new EmployeeInvitation table, which included a status (not_sent, sent, accepted, rejected), the invited_by, and some relevant timestamps. Then I moved the action's behaviour into a model method ($invitation->sendEmail()) and deleted the action.

Dive Deeper with Actions