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This was tested under Linux. We conditionally compiled the code to interface the shell's I/O handlers to Linux's console. The GNU debugger (GDB) was used to find and correct the errors that occurred. Testing simply involved testing each of the shell commands to check that they worked as documented with input values designed to produce errors. After testing and debugging the shell was deemed to be a stable part of the system.

Testing The Filing System

This again was tested under Linux and used the previously tested shell as a user interface. A large file was used to simulate a device in the filing system and using this and the filing system shell commands, we were able to find and correct the many bugs that appeared during the testing. The filing system is a complicated piece of software which contained many bugs when first written. The final test bed which combined the shell and the filing system running under Linux was deemed sufficiently stable to be used as part of the installation process. It was used to copy modules from Linux where they were compiled, to our own filing system and also to retrieve system logs from our filing system back to Linux.

Keyboard Driver

This was tested under DJGPP with a conditional compilation to include code to install the keyboard interrupt handler in the DJGPP dos extender. This enabled us to find the few bugs that existed in the keyboard driver. Overall, we found that the keyboard driver was very stable.

Hard Disk and Floppy Disk Driver

These were tested using a similar method to that employed when testing the keyboard device driver. The hard disk driver was developed using this test system to find bugs as it was written. Overall, these two modules were found to be stable.

The Initialisation Process

This was tested using NuMega's Soft/ICE debugger. Because of the complexity of the boot sector and startup code, many bugs were found and corrected in this way. The initialisation process, after debugging, was found to be very stable.

Testing On Different Machines

One of the basic methods we employed was to test our operating system on as many different hardware configurations as possible. This revealed only one major bug which was with enabling the A20 gate and was found on a PC which had a particularly old and slow chipset. This was soon diagnosed and appropriately fixed.

Testing Internal To The System

These tests were actually run under the operating system and served to test the extent and compatibility of the emulation subsystem. This was achieved by running an operating system (in this case MS-DOS) under a virtual machine and then running programs designed to test the virtual hardware.

PC-Doctor

This program is designed to test the hardware of a PC at the lowest level, i.e. by directly talking to the hardware. Running the system test enabled us to see what devices did not perform properly in the virtual environment. The devices it tested were:

Virtual PIC - This failed on parts of the PIC that were not virtualised. The other parts passed successfully.
Vitrual PIT - This failed on some aspects of testing channel 2. All other features of the PIT worked successfully.
Virtual CMOS - This failed on the Periodic and Alarm Interrupts. All other features of the CMOS including the real-time clock passed successfully.
Virtual DMA - This failed on the tests because the virtual DMA was not designed to actually transfer data, only store the values written to the chips.
Virtual Hard Disk - Although this does not actually test the register level controller, the BIOS level functions are tested thoroughly and these all passed.
Virtual Keyboard - This passed all tests successfully.
Virtual Speaker - This passed all tests successfully.
Virtual Video - The MDA emulation worked correctly but bugs were found in the graphics mode emulation of the CGA device.
Virtual BIOS Data Area - This holds configuration information about the virtual machine and this information was correctly reported by PC-Doctor.

We also tested the virtual machine with a program called `CheckIt' which found many of the same problems.

Other Software Tested

Microsoft Windows 3.0 - This was run in Real-Mode and successfully worked. Because of the nature of this program it fully utilises the hardware of the machine and this shows the level of compatibility that we attained.
Fractint - This tested the graphical capabilities of the CGA emulation and showed very few bugs.
WordPerfect 5.1 - This failed to work for an indeterminate reason. We believe it was to do with interaction between the virtual keyboard and the virtual BIOS.
MS-DOS Dosshell - This almost worked apart from some graphical errors and an inability to select menus.