One production system for a multi-site infrastructure contractor’s machines, sites, employees, attendance, payroll, inventory, purchase orders and statutory reports.
The machine log, diesel register, attendance sheet, stock book and salary calculation lived in different books kept by different people. They described the same operation, but nothing reconciled them.
A machine could move sites. An employee could join, shift or leave. A stock entry could be corrected after later issues had already been recorded. Every report depended on the system answering what was true on a past date, not only what is true now.
Purchase orders were typed by hand onto letterhead. The result had to work as software and as a printed business record.
A connected operating record from daily entry to payroll and reporting.
Where operational truth can quietly drift if the model is wrong.
Running hours come from the meter delta: closing minus opening. A mismatch flag appears when the entered numbers disagree with that result. Before this, all 429 rows had been computed by hand.
The opening chain recomputes live. When an admin corrects a historical meter reading, every later day reads the corrected chain instead of preserving stale derived values.
Joining, shifting and leaving write employee_site_periods. That makes “who was at this site on the 7th?” answerable for any past date, without overwriting history with the employee’s current site.
An independent audit found that an employee created with no date of joining was silently quarantined: created fine, listed fine, absent from every roster, and rejected by attendance. That was the exact symptom the client had reported that week.
Opening 10, issue 8, then a backdated count of 2 drove the stock book to −6. Because the issue picker filters on-hand > 0, the part then vanished from the picker.
A separate adjustment labelled “set to 5” was adding 5 instead. Both behaviours were found and fixed before they reached a balance anyone relied on.
Purchase orders print on the real Techcon letterhead with the GSTIN branch list and the company stamp. Print geometry is part of the acceptance criteria.
A print-only table-layout: auto silently dropped the Grand total and Status columns from the register when a purchase order had about six line items. Headers remained; values disappeared. The test now renders the actual PDF and asserts on extracted text and page geometry. A regex over source cannot detect a column that never makes it onto the page.
A three-way audit across 23 commits and about 7,800 inserted lines returned 15 findings. Four were regressions introduced that same day.
The negative evidence mattered too. The review confirmed that payroll cannot omit or double-pay anyone, and that a person present on two site rosters cannot be paid twice.
Show us the registers, spreadsheets and hand-offs that hold the operation together. We will map where a custom system would pay for itself.