phpvms/app/Database/factories/ExpenseFactory.php

<?php

use App\Models\Enums\ExpenseType;
use Faker\Generator as Faker;

$factory->define(App\Models\Expense::class, function (Faker $faker) {
    return [
        'id' => null,
        'airline_id' => function () {
            return factory(App\Models\Airline::class)->create()->id;
        },
        'name' => $faker->text(20),
        'amount' => $faker->randomFloat(2, 100, 1000),
        'type' => ExpenseType::FLIGHT,
        'multiplier' => false,
        'ref_class' => \App\Models\Expense::class,
        'ref_class_id' => null,
        'active' => true,
    ];
});