I tried creating a unit test for my User service class, however when I run php artisan test this errors are thrown, I have no idea about this since I’m a newbie in unit testing.
The code works perfectly in controllers, this errors only happens in tests:

This is my UserTest class:

<?php

namespace TestsUnit;

use AppServicesUserService;
use PHPUnitFrameworkTestCase;

class UserTest extends TestCase
{
    protected $userService;

    protected function setUp(): void
    {
        parent::setUp();

        $this->userService = app(UserService::class);
    }

    public function test_create_user(): void
    {
        $userArray = [
            'nome' => 'John Doe',
            'email' => '[email protected]',
            'login' => 'johndoe',
            'status' => 1
        ];

        $user = $this->userService->create($userArray);

        $this->assertTrue($user->email === $userArray['email']);
    }
}

Command executed:
php artisan test

Error received:

 FAIL  TestsUnitUserTest
  ⨯ create user                                                                                                                                                0.05s  
  ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────  
   FAILED  TestsUnitUserTest > create user                                                                                                                  Error   
  Call to a member function connection() on null

  at vendorlaravelframeworksrcIlluminateDatabaseEloquentModel.php:1850
    1846▕      * @return IlluminateDatabaseConnection
    1847▕      */
    1847▕      */
    1848▕     public static function resolveConnection($connection = null)
    1849▕     {
  ➜ 1850▕         return static::$resolver->connection($connection);
    1851▕     }