Testing URIs not working

[brownh@hartford-hwp.com (Haines Brown)]

Every step toward getting packages installation to work has been like
pulling teeth. Please be patient.

I want my /etc/apt/sources.list to support the installation of testing
packages, and so I appended the line:

  deb http://ftp.debian.org testing main

But when I run "# aptitude update" with it, I get this error:

W: Couldn't stat source package list http://ftp.debian.org
testing/main Packages
</var/lib/apt/lists/ftp.br.debian.org_debian_dists_testing_main_binary_i386_Packages> (2 No such file or directory)   

I tried these addresses as well:
deb http://ftp.br.debian.org/debian/ testing main
deb http://debian.teleglobe.net/non-US/ testing/non-US main

I discovered that my adding a URI for testing packages to
/etc/apt/sources.list and then running "# aptitude update" had no effect
on the files listed in in /var/lib/apt/lists.

Should it? That is, after running "#aptitude update", should a new
line appear like the one that the Warning above reports not finding?

This happened to me before when I needed to register the location of
a local repository of deb files on my machine. For a long while, I
got the same warning when I ran "#aptitude update", that it couldn't
stat the URI. After a while, it mysteriously popped up in
/var/lib/apt/lists ("_storage_debs_Packages") and my problem ceased. 

How do I force apt to register the testing address in
/var/lib/apt/lists?

Haines Brown