Laravel testing errors: Directory not found

I've been working with Laravel a lot lately, and I hit a (really basic, in hindsight) error that didn't have a good Google search result, so I thought I'd throw it up for others.

When running php artisan test, it was throwing this error:

Test directory "/var/www/osw/osw-asks/./tests/Unit" not found

Very obviously, it's because it's looking for a directory and unable to find it. But why? In my case, it was because I don't have any unit tests yet (only feature tests), so I deleted "Unit." But the default artisan test command is looking for Unit, ergo it's erroring. To fix it, just create an empty "Unit" folder. The same, I assume, would apply if it thought you were missing the Feature folder.