BuildJuniorFull-stackAuto-graded

Software Engineer: Add a discount without changing any other price

Add a residents’ discount to an old ferry booking system without changing any other price.Use Claude Code to add a residents' discount to a ferry company's 2016 fare engine and its booking page, without changing any other price by a cent. Two colleagues send requirements while you work. About 30 minutes, in English or Italian.

30 min

javascript, node

Start lab

You're done when

Checkout charges every booking in which nobody qualifies exactly what today's engine charges (for the history, its charged_cents).
Residents get the discount as TICKET.md and the team's messages define it, rounded the way you decided.
The booking page shows exactly what checkout charges, for every booking, residents included.
Your tests check that today's prices stay exactly the same, that the new rule works and that the page shows what checkout charges: they pass on a correct engine and fail on broken ones.
signoff.json records your rounding decision, with numbers that match what your engine does.

What it measures

Checking legacy behaviour before changing itPinning today's prices with a replay of real bookings before the agent touches the engine.

Turning a rule into code preciselyWho, which legs, which part of the price, and how it rounds, briefed to the agent exactly.

One price on the page and at checkoutFinding the page's own copy of the price logic and making both sides agree.

Owning the decisionChoosing the rounding yourself, with a reason, instead of leaving it to the agent.

Proof with real numbersTests that catch broken engines, and a sign-off whose numbers come from a real run.

Your environment

Terminal + editorA full shell in the browser

Claude CodePre-authenticated, no key setup

Isolated microVMYours alone, wiped afterwards

Start this lab

30 min

Start labYou'll sign in to Anthropos to start. The lab opens in a private cloud workspace with Claude Code ready to use.

AI Labs is part of Anthropos Workforce. Not on your plan yet? Book a demo