Refactor code you have never seen, with a model

Hard45 minFree, no account

An 800-line file, no tests, and a model that will happily rewrite all of it.

The question

You are handed a single 800-line module that computes shipping costs. It has no tests, three nested conditionals eight levels deep, and a comment that says "do not touch. See INC-4471".

A product change requires a new rule. Use a model to make the change safely.

45:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.

Stuck?

0 of 3 hints taken

The worked solution

written by a person · not a grade

Score yourself

0 of 5 marked

Built a characterisation harness before changing anything30
Distinguished freezing behaviour from asserting correctness20
Small verified steps rather than a wholesale rewrite25
Split what to delegate from what to keep, with reasons15
Respected the incident-marked code10

We run no AI here and nothing on this page grades you. The score is yours, and the useful number is the one you get on the same problem a month from now, cold.

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