Is it advisable to let someone test (hack) your website's security with full force?

We know that all websites should use iron security against user input for any type of website, even just an online catalog should have some level of security, and also that anybody could pick your website to hack at any given moment in time.

The question is: Do you think it's advisable to put your website up, especially for hackers, to 'try it with all they've got'? Or, will it really mess up things so bad that it can't be recovered?

Reasons:

1- Test your website security

2- You'll know which security mistakes not to repeat

3- Your website can gain strength by closing up the security holes

This may sound like a silly idea, but I think it could improve beginner's idea about website security and exactly how little a hacker needs to actually mess up your system.

My brother is into networking/hacking and things, and he's going to try hacking one of my best projects with full force. I'm a little unsure about it...