invoiceninja/database/factories/PurchaseOrderInvitationFactory.php

<?php

namespace Database\Factories;

use Illuminate\Database\Eloquent\Factories\Factory;
use Illuminate\Support\Str;

class PurchaseOrderInvitationFactory extends Factory
{
    /**
     * Define the model's default state.
     *
     * @return array
     */
    public function definition()
    {
        return [
            'key' => Str::random(40),
        ];
    }
}