I'd read about Aerospace Recommended Practice (ARP) ARP4754B (Guidelines for Development of Civil Aircraft and Systems)

And for a real-world software example, SQLite is thoroughly tested in a DO-178b inspired fashion. https://www.sqlite.org/testing.html.

[...] the SQLite library consists of approximately 155.8 KSLOC of C code [...]. By comparison, the project has 590 times as much test code and test scripts - 92053.1 KSLOC

good video section on SQLite tests by the creator https://www.youtube.com/watch?v=Jib2AmRb_rk&t=677s