It works

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class Test extends Model{

	protected $fillable = ['text'];	

	public static function boot()
    {
        parent::boot();

        parent::observe(new \App\Http\Observers\TestObserver);
    }

}

But when i put this code on a Service Provider... dont works...

<?php namespace App\Providers;

use Illuminate\Support\ServiceProvider;


class TesteServiceProvider extends ServiceProvider {

	/**
	 * Bootstrap the application services.
	 *
	 * @return void
	 */
	public function boot()
	{
		\App\Test::observe(new \App\Http\Observers\TestObserver);
		
	}

	/**
	 * Register the application services.
	 *
	 * @return void
	 */
	public function register()
	{
		//
	}

}

my app.php

'providers' => [

		/*
		 * Application Service Providers...
		 */
		'App\Providers\AppServiceProvider',
		'App\Providers\EventServiceProvider',
		'App\Providers\RouteServiceProvider',
		'App\Providers\CourseServiceProvider',		
		'App\Providers\TestServiceProvider',

Someone knows why?