Unit 18: Validation, Failure Analysis, and Design Defense

The final unit does not reward hiding the messy part of development.

You will take one Version 1 failure, trace it to the first meaningful divergence, make a controlled revision, and prove that the correction does not break previously passing behavior.

Then you will defend the finished system against its own requirements.

Your final dossier should make the complete chain visible:

problem -> requirements -> architecture -> implementation
        -> tests -> failure -> root cause -> revision
        -> regression evidence -> limitations -> defense

That chain is the capstone product. The code is one critical part of it.