Xpressengine\Register\Container::get PHP Method

    public function get($key, $default = null)
    {
        $class = $this->arrClass;
        return $class::get($this->items, $key, $default);
    }

 public function testAdd()
 {
     $container = new Container('\\Illuminate\\Support\\Arr');
     $key = 'uiobject/xpressengine@select';
     $container->add($key, 'My\\Class\\Select');
     $this->assertEquals('My\\Class\\Select', $container->get($key));
 }