Testing internal HTTP Request - laravel

Question

Hello Laravel Developers,
Today i'm facing some seriously but not at all issue related to testing in Laravel Framework.
See the following code example:
<?php
use App\Http\Controllers\Controller;
use App\Http\Requests\Api\TokenRequest;
use App\Repositories\ExceptionRepository;
use GuzzleHttp\Client;
use Illuminate\Http\JsonResponse;
class TokenController extends Controller {
public function __invoke(TokenRequest $request) : JsonResponse
{
$http = new Client;
try {
$response = $http->post(env('OAUTH_DOMAIN', 'https://oauth.application.com') . '/oauth/token', [
'form_params' => [
'grant_type' => 'password',
'client_id' => env('PASSPORT_PASSWORD_CLIENT_ID'),
'client_secret' => env('PASSPORT_PASSWORD_CLIENT_SECRET'),
'username' => $request->input('email'),
'password' => $request->input('password'),
'scope' => '*',
],
]);
$token = json_decode((string) $response->getBody(), true);
return response()->json([
'message' => 'Token retrieved successfully.',
'token' => $token,
]);
} catch (Throwable $throwable) {
ExceptionRepository::emergency('Something went wrong.', $throwable);
return response()->json([
'message' => 'Token can\' be retrieved.',
'error' => 'Internal server error'
], 500);
}
}
}
This code seems fine but when you're testing you always get internal server error. The TestCase is the following:
<?php
use App\Models\User;
public function test_token()
{
$user = User::factory()->create()->first();
$response = $this->json('POST', '/api/token', [
'email' => $user->email,
'password' => 'password',
]);
$response->assertStatus(500);
}
My ideas about why this happens is because the enviroment variable OAUTH_DOMAIN is different of the right application URL when the code is running via PHPUnit.
In other hand when i try this controller i just need start two instances of artisan serve because when the framework do a internal request it keep frozen and stuck for infinite time. The OAUTH_DOMAIN variable is always the second port of the artisan instance.
Someone know how to face this issue?