Invalid Argument Exception - Laravel Unit Testing - laravel

Question

I am running a unit test to check that
View page exists
AssertSee that text appears on the page and with a string limit
I am getting an invalid argument exception:
1) Tests\Feature\ViewAllPostTest::testCanViewAllPosts
InvalidArgumentException: You requested 1 items, but there are only 0 items available.
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Support\Arr.php:472
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Support\Collection.php:1486
C:\projects\car-torque-laravel\database\factories\PostFactory.php:12
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Database\Eloquent\FactoryBuilder.php:274
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Database\Eloquent\FactoryBuilder.php:292
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Database\Eloquent\Concerns\GuardsAttributes.php:122
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Database\Eloquent\FactoryBuilder.php:300
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Database\Eloquent\FactoryBuilder.php:219
C:\projects\car-torque-laravel\vendor\laravel\framework\src\Illuminate\Database\Eloquent\FactoryBuilder.php:178
C:\projects\car-torque-laravel\tests\Feature\ViewAllPostTest.php:19
My source code is as follows:
Test Function
namespace Tests\Feature;
use App\Post;
use Tests\TestCase;
class ViewAllPostTest extends TestCase
{
/**
* #group posts
*
* #return void
*/
public function testCanViewAllPosts()
{
//arrange
$post = factory(Post::class)->create();
//action
$response = $this->get('/posts');
//assert
$response->assertStatus(200);
$response->assertSee($post->body);
$response->assertSee(str_limit($post->body));
}
}
Factory Class
use App\Post;
use App\User;
use Faker\Generator as Faker;
$factory->define(Post::class, function (Faker $faker) {
return [
'body' => $faker->text,
'user_id' => User::all()->random()->id,
'created_at' => now(),
'updated_at' => now(),
];
});

Answer 1

'user_id' => User::all()->random()->id,
In the above line of your factory, you want random id form your users table. But have you created any User before running the test. At least a user should be created before creating post using post factory.