[Lumen] Unit testing issue with request content

Hey guyz,

I'm running into an issue while unit testing a controller, at some point during the unit testing run, the content of my requests are removed.

use Illuminate\Support\Facades\DB;

class AccountControllerTest extends TestCase
{
    public function testInsertAchievedCAs()
    {
        $response = $this->call(
            'POST', '/account', [], [], [], [], 'AAAAA'
        );
        $this->assertResponseOk();
    }
}

class AccountController extends Controller
{
    /**
     * @param Request $request
     *
     * @return string
     */
    public function insertAccount(Request $request)
    {
        $content = $request->getContent();
    // While running unit tests $content === ""
    // While running normally through postman for example $content === "AAAAA"
   }     
}

So basically the app is working as intended when using the browser, but the unit tests are not working as intended, did any of you run into this issue ? Or am I missing something ?