php - Adding an entry in db with Slim and Eloquent

one text

I'm starting a project using Slim and Eloquent, the connection with my database is working perfectly. My problem is that I can't add an entry to my tests table. Here is my Model

use Psr\Http\Message\ResponseInterface as Response;
use App\Domain\Test\Test;
use Illuminate\Http\Request;

class NewTestAction extends TestAction {

    protected function action(): Response {

        $data = $this->request->getParsedBody();
        $test = new Test;
        $test->id = $data["id"];
        $test->txt = $data["txt"];
        $test->save();
        return $this->respondWithData($test);

    }

}

It works if I put the values directly in the code, like this

$test->id = 1;
$test->txt = "test";

I'm using Postman to test my code, I got that Error

{
"statusCode": 500,
"error": {
    "type": "SERVER_ERROR",
       "description": "ERROR: Trying to access array offset on value of type null on line 18 in file /home/fiona/my_micro_service/my_micro_services/src/Application/Actions/Test/NewTestAction.php."
    }
}

How can I insert a basic entry to my db ?

Update with my table structure and Model

    TABLE tests
   (id int(11),
   txt VARCHAR(255),
    updated_at date,
    created_at date);

Model :

namespace App\Domain\Test;
                        
class Test extends \Illuminate\Database\Eloquent\Model {
}