Problem : notify-send command is not showing up notification even though the log file is created.
Contents of /home/user/test
echo 'test job, reporting...'
notify-send 'This is a simple notification Sir'
Contents of /etc/init/myjob.conf
description "test job"
start on runlevel 
To check for any syntax error :
$ init-checkconf myjob.conf
In order to run the above .config file i used :
$ sudo start myjob
to view the contents of log generated :
$ sudo gedit /var/log/upstart/myjob.log
Best How To :
This is not an Upstart problem at all. You are trying to send Desktop Notifications using system job which is executed in an environment having no refference to you desktop session namely it is missing
DISPLAY along with other environmental variables.
You could use us session job instead (recommended) or gain understanding on Linux permissions, session and environments and define needed enviromental variables in your system job configuration file. You might find some useful hints in those two threads related to sending desktop notifications from system cron job. 1 and 2