unable to locate factory with name [default] [Subject]

i just want some dummy data that i can loop out from my data base but when i try to using the seeder i get this error.."unable to locate factory with name [default] [Subject]".. the code i run is php artisan db:seed --class=SubjectSeeder

//this is my ModelFactory.php

$factory->define(App\Subject::class, function (Faker\Generator $faker) {
return [
    'name' => $faker->name,
    'code' => $faker->str_random(3),
    ];

});

//this is my SubjectSeeder.php

public function run()
{
    $subject = factory(Subject::class)->make();

    Product::create([
        'name' => $subject->name,
        'code' => $subject->code
    ]);
}

//this is my subject.php

class Subject extends Model
{
    protected $fillable = [
        'name', 'code',
    ];
};

via Chebli Mohamed