Interfering with FireFox's Print Manager

 

Summary

While printing any document in FireFox Internet browser, a dialog box appears while the document is being sent to the printer allowing the user to cancel the print job. After pressing the 'Cancel' button, however, the dialog box immediately disappears but the will printer still print the entire document.

Application Description

Mozilla's FireFox is an Internet browser available for Linux, MacOS, and Windows. At the time of writing this presentation, FireFox was still pre-1.0 (meaning that it was still a preview release for testing purposes).

Test Design

This example demonstrates the use of Interference testing. One of the most unstable times of using any program is when canceling a function that is already in progress. Interfering with the process tells the program to discontinue what it is doing and revert back to its previous state. A task like this might involve coordinating the processor, RAM, CD/Hard drives, and other software, all during which the computer itself will still need to continue performing other tasks.

FireFox allows users to print out web pages. Knowing that we can print, with Interference testing in mind, we begin thinking of how we can interfere with the print job. So, what we will do is to start a print job (a large one that gives us time to observe the results) and cancel that print job as it is being sent to the printer. We then observe how the application deals with the canceled print job.

Interference testing is where many bugs are found simply because these types of processes are tightly tied in with the uniqueness of a hardware setup and the way that hardware is being utilized by other running software.

Performing the Test

  1. Open Mozilla FireFox.
  2. Navigate to the page http://www.linux-praxis.de/lpic1/lpi101/1.102.2.html:

    This is a German-language site about installing bootloaders for operating systems.

  3. Once the page has loaded, use File->Print... or Ctrl-P to open the Print Options box:

  4. Once the Print Options box is open, make sure that the correct print settings are selected:

  5. Press 'OK' to begin printing the document.
  6. Once the document starts being sent to the printer, press the 'Cancel' button to stop the print process:

Results/Relevance

It actually does not matter when we press 'Cancel' on this dialog box, the printing process will still continue. The dialog box will immediately disappear, but after a moment the printer will begin printing and will actually print the entire document. Unless the user has time to cancel the print job within the actual printer, they will have just printed about 8 pages (depending on settings) with graphics.

It is not just this website that causes this problem. This website was chosen randomly for its document length so that it would take a considerable amount of time to send to a printer.

The inability to cancel a print job can lead to problems with printer availability (especially on a networked printer), loss of expensive ink and toner, and loss of paper. If the print job was a long or color-intensive one (such as printing a color photograph on a high quality printer), the amount of ink wasted would be especially expensive. Until the entire print job is recieved by the printer, it is still the responsibility of the application to handle a cancellation.

Whether the browser or the printer work well together for printing documents or not (in terms of how the document is printed), Interference testing helped us locate an area that is especially important, how well the browser can tell the printer to stop printing.

Similar Tests/Additional Notes

During this time before FireFox is officially released, it is a Software Testing student's dream-come-true. Explore this pre-release software from many different testing angles and take advantage of this excellent showcase of beta software while it is available.

Configuration Notes

Testing Mozilla's FireFox v0.9.1 on:

Created 19 July 2004 for the CSTER

All images and written material ©Copyright Sam Oswald 2004

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