A simple htaccess modification can solve a web site change for you. If you want to create a new directory for whatever reason and redirect the old directory to the new one, this will get it done:
## /testa/ to /testb/ RewriteEngine on RewriteRule ^testa/(.*)$ testb/$1 [R,L]
This will rewrite the directory and all the files in the directory as well.
Live example usage: