mega-plant/lib/running-month.test.ts

// The month rules on the running-cost pages.
//
// Run: node --import tsx --test lib/running-month.test.ts
//
// Two rules that keep three screens from disagreeing:
//
//   1. A year-to-date figure counts the months that have HAPPENED. A premium or an
//      instalment for a month that has not happened yet is a rate on file, not money the
//      client has spent, so it is not part of the year to date.
//
//   2. The Overview and the financing register read the SAME finance rule, so the
//      fleet's finance for a month is the same rand on both.
//
// A third one is checked here because it is the whole point of the exercise: the
// insurance page and the Overview must quote the SAME year to date for insurance.
import { test } from "node:test";
import assert from "node:assert/strict";
import { elapsedMonths } from "./income-month";
import { buildInsuranceRows, buildRunningRows } from "./rows";
import { financeByAsset, fleetFinanceByMonth, machineRunningCosts } from "./running-costs";

const asset = (id: string, code = "TLB01") =>
  ({
    id,
    code,
    name: code,
    category: "Plant",
    type: "",
    gl_account: "",
    supplier: "",
    monthly_excl: 0,
    monthly_incl: 0,
    purchase_value: 0,
    is_provisional: false,
    is_active: true,
  }) as any;

const rate = (assetId: string, from: number, to: number, amount: number) =>
  ({
    id: `r-${assetId}-${from}`,
    asset: assetId,
    year: 2026,
    month_from: from,
    month_to: to,
    rate: amount,
  }) as any;

const term = (
  assetId: string,
  installment: number,
  settled = false,
  end: [number, number] = [2026, 12],
) =>
  ({
    id: `t-${assetId}`,
    asset: assetId,
    installment,
    is_settled: settled,
    start_year: 2026,
    start_month: 1,
    end_year: end[0],
    end_month: end[1],
  }) as any;

/** Rands to the cent — the monthly figures are floats and must not be compared exactly. */
const cents = (n: number) => Math.round(n * 100) / 100;

test("elapsed months count the year as it stands", () => {
  assert.equal(elapsedMonths(2026, new Date("2026-11-05T09:00:00")), 11);
  assert.equal(elapsedMonths(2026, new Date("2026-01-15T09:00:00")), 1);
  // A year that is over is a whole year.
  assert.equal(elapsedMonths(2026, new Date("2027-03-01T09:00:00")), 12);
});

test("the insurance YTD stops at the month that has happened", () => {
  const rates = [rate("a1", 1, 0, 1300)];
  const full = buildInsuranceRows([asset("a1")], rates);
  const toNovember = buildInsuranceRows([asset("a1")], rates, 11);

  assert.equal(full[0].ytd, 1300 * 12, "a whole year, when the whole year is the window");
  assert.equal(toNovember[0].ytd, 1300 * 11, "Jan-Nov only");
  assert.equal(toNovember[0].chargedMonths, 11, "the months the YTD actually sums");
  assert.equal(toNovember[0].coveredMonths, 12, "the year's coverage is still reported in full");
  assert.equal(toNovember[0].months[10], 1300, "November still carries its premium");
});

test("a month with no premium on record is unknown, not free", () => {
  // Insured from June only: January-May are unknown, and the YTD says so.
  const rows = buildInsuranceRows([asset("a1")], [rate("a1", 6, 0, 1300)], 11);
  assert.equal(rows[0].months[0], null, "January has no premium on record");
  assert.equal(rows[0].ytd, 1300 * 6, "June to November, and not one rand less");
  assert.equal(rows[0].chargedMonths, 6);
});

test("a live agreement runs to the current month; a settled one with no paid-off date costs nothing", () => {
  const months = fleetFinanceByMonth(
    // The settled one has NO paid-off date: we cannot say when it stopped, so it is
    // charged for nothing at all.
    [term("a1", 1000), term("a2", 500, true, [0, 0])],
    11,
  );
  assert.equal(months[0], 1000, "January: the live agreement only");
  assert.equal(months[10], 1000, "November: still the live agreement");
  assert.equal(months[11], 0, "a month past the horizon is not charged");
  assert.equal(
    months.slice(0, 11).reduce((s, v) => s + v, 0),
    11 * 1000,
    "the year's instalments",
  );
});

test("a settled agreement whose paid-off date is still ahead is still paying", () => {
  // "Settled" means paid off, OR will be paid off by the paid-off date — so the money
  // is still moving until then.
  const months = fleetFinanceByMonth([term("a2", 500, true, [2026, 12])], 11);
  assert.equal(months[10], 500, "November is still inside its window");
});

test("an agreement paid off in October is charged to October and NOT to November", () => {
  // TLB06: settled, paid off in October 2026. The instalments it was paying in
  // January-October are real spend and belong in the year; November is not its month.
  const tlb06 = {
    id: "t-tlb06",
    asset: "a1",
    installment: 29036.08,
    is_settled: true,
    start_year: 2023,
    start_month: 9,
    end_year: 2026,
    end_month: 10,
  } as any;
  const months = fleetFinanceByMonth([tlb06], 11);
  assert.equal(months[0], 29036.08, "January is charged");
  assert.equal(months[8], 29036.08, "September is charged");
  assert.equal(months[9], 29036.08, "October is charged");
  assert.equal(months[10], 0, "NOVEMBER IS NOT — the agreement ended in October");
  assert.equal(
    cents(months.slice(0, 11).reduce((s, v) => s + v, 0)),
    cents(29036.08 * 10),
    "ten months of instalments, not eleven",
  );
});

test("a live agreement stops at its own paid-off date", () => {
  // RV04: paid off in November 2026, so it IS charged for November.
  const rv04 = {
    id: "t-rv04",
    asset: "a1",
    installment: 28641,
    is_settled: false,
    start_year: 2024,
    start_month: 1,
    end_year: 2026,
    end_month: 11,
  } as any;
  const months = fleetFinanceByMonth([rv04], 11);
  assert.equal(months[10], 28641, "November is its last month");
  assert.equal(
    cents(months.slice(0, 11).reduce((s, v) => s + v, 0)),
    cents(28641 * 11),
    "charged for every month of the year it was live",
  );
});

test("the register and the Overview read the same finance rule", () => {
  const terms = [term("a1", 1000)];
  const perAsset = financeByAsset(terms, 11);
  assert.equal(perAsset.get("a1")?.[0], 1000);
  assert.equal(perAsset.get("a1")?.[10], 1000);
  // The fleet total is the sum of the per-asset months — never a second rule.
  assert.equal(fleetFinanceByMonth(terms, 11)[10], 1000);
});

test("the Overview's finance year to date IS the financing register's year to date", () => {
  const assets = [asset("a1"), asset("a2", "TLB06")];
  const terms = [
    {
      id: "t-tlb06",
      asset: "a2",
      installment: 29036.08,
      is_settled: true,
      start_year: 2023,
      start_month: 9,
      end_year: 2026,
      end_month: 10,
    } as any,
    {
      id: "t-rv04",
      asset: "a1",
      installment: 28641,
      is_settled: false,
      start_year: 2024,
      start_month: 1,
      end_year: 2026,
      end_month: 11,
    } as any,
  ];

  const { byAsset } = machineRunningCosts(
    { assets, repairs: [], purchases: [], purchaseLines: [], insurance: [], finance: terms },
    11,
  );
  const running = buildRunningRows(assets, byAsset);
  const overviewYtd = running.reduce((s, r) => s + r.byKindYtd.finance, 0);
  const registerYtd = fleetFinanceByMonth(terms, 11).slice(0, 11).reduce((s, v) => s + v, 0);

  assert.equal(cents(overviewYtd), cents(registerYtd), "the two screens must quote the same rands");
  assert.equal(cents(overviewYtd), cents(29036.08 * 10 + 28641 * 11));
});

test("the insurance page and the Overview quote the same year to date", () => {
  const assets = [asset("a1"), asset("a2", "TLB02")];
  const rates = [rate("a1", 1, 0, 1300), rate("a2", 1, 6, 900), rate("a2", 7, 0, 1000)];

  const insuranceRows = buildInsuranceRows(assets, rates, 11);
  const { byAsset } = machineRunningCosts(
    { assets, repairs: [], purchases: [], purchaseLines: [], insurance: rates, finance: [] },
    11,
  );
  const running = buildRunningRows(assets, byAsset);

  const insuranceYtd = insuranceRows.reduce((s, r) => s + r.ytd, 0);
  const overviewYtd = running.reduce((s, r) => s + r.byKindYtd.insurance, 0);
  assert.equal(insuranceYtd, overviewYtd, "the two screens must not be a month apart");
  assert.equal(insuranceYtd, 1300 * 11 + 900 * 6 + 1000 * 5);
});