Debian downgrade from sid to testing

# vi /etc/apt/sources.list

deb http://ftp.debian.org/debian/ sid main non-free contrib
deb-src http://ftp.debian.org/debian/ sid main non-free contrib
deb http://ftp.debian.org/debian/ testing main non-free contrib
deb-src http://ftp.debian.org/debian/ testing main non-free contrib

# vi /etc/apt/preferences

Package: *
Pin: release a=testing
Pin-Priority: 1001

# apt-get update
# apt-get dist-upgrade

References :
Debian downgrade from SID to testing ~ Billy Vera