Add mutation testing in the CI #506

Is your feature request related to a problem?

I’d like to improve ArkScript test suites. We already have coverage, but that only tells us the code was executed, not that it’s correct.

Describe the solution you would like

To improve our tests, I’d like to add mutation testing (along side the existing fuzzing and coverage).

The idea would be to add a job running in parallel with the valgrind job. The idea is to run mutation testing on a single OS with a single compiler, to report how many tests should be improved.

https://www.youtube.com/watch?v=lhcXAnNgzlo

Is it a big modification to the language? Leave it if you don't know

• Breaking change
• Compiler/syntax modifications
• Runtime modifications (standard library, modules, packages...)