Duplicate blog for theme development

Hey guys!

I want to start making my own WordPress theme. No problems there. However: I don’t want to start making changes to my current blog to test the theme. My blog is currently live, so I don’t want my test themes to be visible to the public.

Is there a feature in WordPress that allows me to develop a theme and preview it on my blog without changing the theme on my live blog?

If there isn’t a feature, is there a nice, clean method I could use to duplicate my WordPress blog to a different ‘development’ folder? If I just copy the files I’m sure the page links and such would be corrupted.

Thanks!

Regards,
TheWaste