Even better is to have these web tests run automatically every time I commit code. I use Jenkins for this. Jenkins even fires up a headless desktop so Selenium can run Firefox.

When a web test breaks (especially in some way I can’t reproduce on my local desktop), sometimes it helps to actually see what Jenkins sees as it runs the test. Here’s a quick guide for doing so on an Ubuntu GNU/Linux server.

1. Connect to the remote server using SSH. Install VNC server:
   

   sudo apt-get install vnc4-server

2. On the remote server, become the user tests run as. For example:
   

   sudo su - ci

3. Set a password for the VNC server using the vncpasswd command.
4. Start headless X server by running vncserver. Note the given display. If example.com:1 is included in the output of vncserver, the display is :1.

5. Figure out which port the VNC server is using. I usually do something like

   sudo netstat -nape | grep '^tcp.*LISTEN.*vnc.*'

   Here’s some example output:

   tcp        0      0 0.0.0.0:6001            0.0.0.0:*               LISTEN      107        3099855     13233/Xvnc4     
   tcp6       0      0 :::5901                 :::*                    LISTEN      107        3099858     13233/Xvnc4

   By trial and error, I figured out that 5901 was the port I should use.

6. Port-forward VNC to your local machine.

   1. Disconnect from the server.
   2. Reconnect, including -L10000:localhost:5901 on your SSH command line.
   3. Leave this connection open.

7. On your local machine, connect a VNC client to localhost:10000. An X terminal should be displayed.

8. In the X terminal, run your web tests.

9. When finished debugging, kill the X server using the display noted earlier.

   vncserver -kill :1

I helped them with their Passwordless SSH tutorial, and I like the screencasts in the Vim tutorial.