Cannot find trait inside my test?

I have a trait inside tests\Feature\Traits:

<?php

namespace Tests\Feature\Traits;

trait HasMediaTest
{
    public function test_something_in_the_trait()
    {
        $this->assertTrue(true);
    }
}

It is used like this:

<?php

namespace Tests\Feature;

use Tests\Feature\Traits\HasMediaTest;
use Tests\TestCase;

class UserTest extends TestCase
{
    use HasMediaTest;

    public function test_something()
    {
        $this->assertTrue(true);
    }
}

Both tests pass fine. But in cmd line I get a warning:

 WARN  Class HasMediaTest cannot be found in /Users/panthro/Documents/web/applawred/tests/Feature/Traits/HasMediaTest.php

I have done the usual composer dump-autoload.

Here is the composer file:

 "autoload": {
        "psr-4": {
            "App\": "app/",
            "Database\Factories\": "database/factories/",
            "Database\Seeders\": "database/seeders/"
        }
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\": "tests/"
        }
    },