Inventory import test fails about once a week and never reproduces

Problem Description

test/inventory.test.js fails roughly one CI run in a hundred. The usual message is expected 39 to equal 40 on every imported row gets its own inventory record. Twice this quarter we also saw Error: price is required for SKU-40213 from the other test in the file.

Re-running the job always goes green. The sku in the error message is different every time and never matches anything in the repository. We have never reproduced either failure locally, including with the suite in a loop overnight on one machine.

The failures started when this file was written and have not changed frequency since. src/inventory.js has not been touched in that period and is the code path the nightly supplier feed uses in production. Its input contract is in the comment at the top of the file.

Output Specification

1. Fix test/inventory.test.js so the two tests give the same result on every run, on every machine, forever - not a lower failure rate.
2. Keep both tests and their assertions: forty records for forty rows, and a catalog value equal to the sum of the imported rows. Do not modify src/inventory.js.
3. Write inventory-report.md: what makes one run differ from the next, why both failure messages come from the same cause, and what a reviewer should reject in a future test in this file.

Run node --test before you finish; it must pass.

Input Files

Extract the following files before beginning.

=============== FILE: package.json =============== { "name": "warehouse", "version": "1.4.3", "private": true, "scripts": { "test": "node --test" } }

=============== FILE: src/inventory.js =============== 'use strict';

// Import contract: every row carries a sku that is unique within the batch // and a price of at least 1 (in cents). Rows are keyed by sku. function importRows(rows) { const inventory = new Map(); for (const row of rows) { if (!row.price) { throw new Error(price is required for ${row.sku}); } inventory.set(row.sku, { sku: row.sku, price: row.price, qty: row.qty }); } return inventory; }

function catalogValue(inventory) { let total = 0; for (const item of inventory.values()) { total += item.price * item.qty; } return total; }

module.exports = { importRows, catalogValue };

=============== FILE: test/inventory.test.js =============== 'use strict';

const test = require('node:test'); const assert = require('node:assert/strict'); const { importRows, catalogValue } = require('../src/inventory');

const randomSku = () => SKU-${Math.floor(Math.random() * 100000)}; const randomPrice = () => Math.floor(Math.random() * 10000); const randomRow = () => ({ sku: randomSku(), price: randomPrice(), qty: 1 });

test('every imported row gets its own inventory record', () => { const rows = Array.from({ length: 40 }, randomRow);

const inventory = importRows(rows);

assert.equal(inventory.size, 40); });

test('catalog value adds up the imported rows', () => { const rows = Array.from({ length: 12 }, randomRow); const expected = rows.reduce((sum, row) => sum + row.price * row.qty, 0);

const inventory = importRows(rows);

assert.equal(catalogValue(inventory), expected); });