test.js

// Integration check: 0-floor + CSV round-trip against the real server.
// Run: node test.js   (uses a throwaway CSV via the CSV env var)
const assert = require('assert');
const fs = require('fs');
const os = require('os');
const path = require('path');

const tmp = path.join(os.tmpdir(), `kc-test-${process.pid}.csv`);
fs.writeFileSync(tmp, 'key,quantity\napples,0\noranges,0\npears,0\n'); // keys come from the CSV
process.env.CSV = tmp;
const PORT = process.env.PORT = '34100'; // avoid clashing with anything on :3000
const base = `http://localhost:${PORT}`;
require('./server');

async function post(key, delta) {
  const r = await fetch(`${base}/data`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ key, delta }),
  });
  return (await r.json()).value;
}

const qty = (data, key) => data.find(r => r.key === key).value;

(async () => {
  assert.strictEqual(await post('apples', 1), 1);
  assert.strictEqual(await post('apples', 1), 2);
  assert.strictEqual(await post('apples', -5), 0, 'must floor at 0, not go negative');

  // round-trip: value persisted, GET returns the fixed key list with stored qtys
  await post('pears', 3);
  const data = await (await fetch(`${base}/data`)).json();
  assert.deepStrictEqual(data.map(r => r.key), ['apples', 'oranges', 'pears']);
  assert.strictEqual(qty(data, 'apples'), 0);
  assert.strictEqual(qty(data, 'oranges'), 0);
  assert.strictEqual(qty(data, 'pears'), 3);

  // unknown key rejected (not in the hardcoded list)
  const bad = await fetch(`${base}/data`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ key: 'bananas', delta: 1 }),
  });
  assert.strictEqual(bad.status, 400);

  fs.unlinkSync(tmp);
  console.log('ok');
  process.exit(0);
})();