Answers for "Illuminate\Contracts\Container\BindingResolutionException : Target class [ItemSeeder] does not exist."

IlluminateContractsContainerBindingResolutionException target calss does not exist

Routing namespaces have been updated on Laravel 8.X

On your router, you should define:
use AppHttpControllersTestController;

And then, declare:
Route::get('test',[TestController::class, 'test']);