Lab: The working-day gap, from field note to product

Module 13 · Lab · About 60 minutes · Needs: lessons 1 and 2 of this module (field log, feedback card, ranking, extension point, fork register); basic Python and git

What you are building

Monday 1 June 2026, week 12. Mei inherits the Harbourline deployment on Friday, and with it a patched sla.py that counts working days. Ines decides by 30 June whether the product gets a calendar setting. This lab carries that one gap the whole way: from field notes at all four of Larkfield's customers to a change Ines can review, and from Harbourline's fork to a branch that holds only configuration.

Seven steps, each with a check in plain Python: count the notes, measure the gap, write the card, rank it, build the extension point, test every plug-in against one contract, then prove the customer branch merges cleanly and keep the register honest. There is no model call; nothing here needs one. Harbourline's five sample deliveries come from Lesson 2. Everything at Corran Parts, Ashby Vale Homes and Lowther Estates is simulated and added in this lab, except the holiday dates, which are gov.uk's.