[#163] add test to calc checksum from serialised output

[lowecg]

I've added a simple test and successfully run on JDK 17 and 21.

It doesn't cover compressed or encrypted scenarios yet, but those can be added easily enough

[ptaoussanis]

Thanks for this! I ended up taking a slightly different approach, first making the stress data deterministic and then adding a hash check.

But the principle is the same 👍