Plan a 400-file migration with a model

Hard45 minFree, no account

The work is mechanical, the review is not, and 400 files cannot be read.

The question

Migrate 400 files from a deprecated date library to the platform's built-in date API.

The behaviour must not change. Decide what to automate, what to generate, and how a human can actually review the result.

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

Counted and classified call sites before converting anything25
Used the model to write a codemod rather than 400 diffs30
Separated the semantically risky sites for human work20
A differential harness covering DST and locale boundaries15
A landing strategy that is reviewable and revertible10

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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