I cannot bind the "contact" route to the "contact" method which is existing in the "TestController.php" controller

I cannot bind the "contact" route to the "contact" method which is existing in the "TestController.php" controller

You don't need to include the file extension when you define routes, so your route should be:
Route::get('/contact','TestController@contact');
Then make sure you have a controller with that name in your controller directory:
app/Http/Controllers/TestController.php
namespace App\Http\Controllers
class TestController extends Controller
{
public function contact()
{
// your code
}
}
You can see a working demo here.