Runtime testing framework

[SamTebbs33]

It would be useful to implement a system for testing the kernel at runtime. This would be used to test components of the kernel, such as paging, multitasking and the filesystem.

A possible approach to running a certain testcase would be to boot the kernel in testing mode (perhaps with a build specific for that testcase), have it initialise the component being tested and printing to serial with some predetermined format based on success or failure. A program could then be attached to the kernel's serial port ensuring that the correct output is received.

The results could then be compiled into a testing report.

Possible dependency on #37 if serial output is how we monitor test results.

[SamTebbs33]

https://wiki.osdev.org/Unit_Testing

[SamTebbs33]

https://forum.osdev.org/viewtopic.php?t=17948

[DrDeano]

Not sure if we have the money for that ;)

[SamTebbs33]

Didn't stop me buying an core 2 duo laptop from 2006 😂 £10 well spent

[SamTebbs33]

I've been exploring our options with this. My current design idea is as follows:

• When you want to do a runtime test of the kernel, you build it with zig build -Drt-test=true which then sets a flag in build.zig and builds as normal.
• The source files will check for that flag in the build file (using @build to refer to it) and add some logging specific to testing if the flag is set.
• The new build can be tested with zig build test -Drt-test=true, which will run a test harness.
• This test harness will run zig build run and attach itself to the emulators stdout so that it can capture the serial output.
• The test harness will then check the output to make sure all test logs are emitted and are correct. The results are then printed in a readable way.