I understand the question (now), as asking about self test programs to check a CPU (or its emulation) for correct operation by trying out certain instructions and verifying the results. Does this fit?
Such were plenty. In The Early Days (tm) magazines like Byte, Kilobaud or Micro published such for many new CPUs. It was a very common finger exercise for engineers to write one when adapting to a new CPU. That way one had to look and understand each instruction while creating a clear proof of that understanding. Publishing that was an easy way share (and maybe even earn a few quid).
In addition manufacturers also provided such programs. I remember at least one by Intel for 8085 as part of the ISIS-II system as well as a similar for 6802 by Motorola for their Exorciser (sic!) development system.
So, while Github et.al. may bring some modern recreation, the true treasure trove is as usually buried in all these old magazines of very early days.
(On purpose no links to avoid creating a list answer)
Fun story to be added:
Some bootstrap ROMs for microcomputers contained rather elaborate CPU self test code, able to separate improved CPU versions from their predecessors. One example might be the Siemens PC-MX, a multibus-based 8086 multi-user Unix system. While at the time performing rather well, having a little more punch would have been appreciated. So when NEC brought the V30, I of course tried to use one - except, the boot ROM denied loading the system because of the 'bad' CPU.
Some disassembly later I found that the ROM contained almost two KiB of code testing many instructions and addressing modes including timing, which of course detected the slightly faster execution of a V30.
So yeah, beefing up an Amstrad PC 1512 was a no-brainer; doing the same with a 5 times as expensive professional system failed badly.