sudo apt-get install -y xserver-xorg-video-dummy
$ cat <<EOF | sudo tee /etc/X11/xorg.conf
Section "Device"
   Identifier "test"
   Driver "dummy"
EndSection
EOF
$ sudo -n mkdir -p /etc/lightdm/lightdm.conf.d
$ cat << EOF | sudo -n tee /etc/lightdm/lightdm.conf.d/umaketests.conf
[SeatDefaults]
autologin-user=ubuntu
EOF
$ sudo reboot
$ $ pgrep -a 'unity|compiz'
1824 /usr/lib/unity-settings-daemon/unity-settings-daemon
1841 /usr/lib/unity/unity-panel-service
1960 compiz
1985 /usr/lib/unity-settings-daemon/unity-fallback-mount-helper
$ DISPLAY=:0 xrandr 
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 320 x 240, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm
   1024x768       60.0* 
   800x600        60.0     56.0  
   640x480        60.0  
   680x384        60.0  
   512x384        60.0  
   400x300        60.0     56.0  
   320x240        60.0