Where is your Tests directory?
Assuming everything goes through the index.php file, you might want a .htaccess config to force that, with an exception for the Assets folder, whose contents you'll want to access directly, most likely. Here's what I used for my cwrblog code (in which I used essentially a MVC-style directory structure):
RewriteRule ^favicon static/favicon.ico
RewriteRule !^static index.php
ErrorDocument 404 /static/404.html