It is always good when you can test your features fast. But sometimes it’s literally hard and takes a lot of time to test something in Magento. When you make one little change in code and want to test it, it can take much more time to test it rather than make the change itself. Nevertheless it’s a common situation taking into account the complexity of Magento.
I have often seen custom shell scripts on Magento instances, be it a script testing out some code snippet or an attribute installation script which hadn’t made it’s way to a separate module. This will create a mess in the files structure as there are quite a lot files already residing in the root folder. There is, however, the dedicated place where these scripts should be placed and this place is the ‘shell’ folder in the root of every Magento installation