[root@rock ~]# pacman -Sy testing/firefox
:: Synchronizing package databases... 
 testing                  [########################################################] 100%       0K    22.8K/s  00:00:00
 current                  [########################################################] 100%      70K   571.0K/s  00:00:00
 extra                    [########################################################] 100%     267K   753.7K/s  00:00:00
 unstable                 [########################################################] 100%      12K   293.1K/s  00:00:00
:: community is up to date

Remove:  mozilla-firefox

Targets: firefox-2.0-1

Total Package Size:   9.4 MB

Proceed with upgrade? [Y/n] 

:: Retrieving packages from testing...
 firefox-2.0-1            [########################################################] 100%    9575K   713.8K/s  00:00:13

checking package integrity... done.
removing mozilla-firefox... done.
loading package data... done.
checking for file conflicts... done.
installing firefox... done.