Laravel 5.1 - barryvdh / laravel-dompdf, PDF-file downloading is not working properly


I have installed 'barryvdh/laravel-dompdf' using composer and added these lines

'PDF'=>  Barryvdh\DomPDF\Facade::class

to 'app.php' file in 'config' folder and also created PdfController, like this

namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Http\Requests;
use App\Http\Controllers\Controller;
use App;
use PDF;

class PdfController extends Controller
    public function invoice()
        $pdf = App::make('dompdf.wrapper');
        return $pdf->stream('testfile')

now the code works fine , contents are show in browser in pdf format, but when i download this file, the file doesn't have any extension.I tried to modify the line containing return code like

return $pdf->stream('testfile.pdf')

But now, page directly provides file to download with name 'document.pdf' which shows error while downloading,(dont konw how and from where this name 'document.pdf' came from). Also i m working on localhost.

What do you want to do with pdf ? To show in browser or to download to disc? this is example where pdf is downloaded

return $pdf->download('pdfName.pdf');

example from my code where i show notebook information in pdf

   $laptop = Notebook::findOrFail($id);
        $data['laptop'] = $laptop;
        $pdf = \PDF::loadView('pdf.detaljiLaptop', $data);

        return $pdf->download($laptop->modelName.' Computers.pdf');