Laravel RefreshDatabase doesn't work in testing

In order to move my current Laravel 5.5 project to the latest version, I was trying to setup some tests (I've never done that before).

To do so, I added <env name="DB_CONNECTION" value="mysql_testing" /> in the phpunit.xml, under the <php> section, and created a copy of the current mysql configuration under config/database.php naming it mysql_testing, which has 'database' => env('DB_NAME_TESTING', 'forge') .

In the .env file I put DB_NAME_TESTING=testDB. The database exists, is empty and the user has all permissions on it.

I haven't created any Test, yet, just tried the Examples provided by Laravel. If I run the tests as they are, they all pass. If I add the RefreshDatabase trait on them, instead, I get

ErrorException : Trying to access array offset on value of type int
C:\[path to project]\vendor\symfony\console\Input\ArrayInput.php:135

which corresponds to } elseif ('-' === $key[0]) {.

After a bit of tracing, I found out that the $key is 'migrate:fresh', which is the Artisan command that RefreshDatabase is trying to run. In later versions this segment has been replaced with } elseif (str_starts_with($key, '-')) {, but this is only available since PHP 8, and I'm currently stuck with PHP 7.4.

My question now is: what am I doing wrong in setting up my testing database?

via Chebli Mohamed