URL Redirection but keep url

Question

I have a url test.html and a url test2.html. What I am trying to do is have it redirect test.html to test2.html but keep the same url. so far I tried this:

RewriteEngine on 
RewriteRule ^test.html$ test2.html

and put it in a .htaccess file which I put in the same folder as the other two files. It just caused the whole site not to load at all.