MediaWiki anti-bot coding

I want to modify MediaWiki handling of user registration to add an anti bot check.

It looks like the addNewAccountInternal() method in the includes/SpecialUserlogin.php file is the right place to do it.

The problem is that nothing I change in that file seems to make any difference. Not even removing that file. I didn't install any kind of cache in the server.

I hav开发者_Go百科e already written the client side JavaScript code in the includes/templates/Userlogin.php file and it works as expected.

What am I missing?

The same file exists in includes/specials and there the modifications work.