DeepSeek Harness 最佳實踐：完成兩個可核驗的修復

create_harness_lab() {
mkdir harness-lab || return
cd harness-lab || return
cat > orders.csv <<'CSV'
id,status,cents
A,paid,1200
B,refunded,700
C,paid,800
D,pending,400
CSV
cat > report.mjs <<'JS'
export function totalPaid(csv) {
  const rows = csv.trim().split(/\r?\n/).slice(1);
  return rows.map(row => row.split(','))
    .filter(([, status]) => status !== 'pending')
    .reduce((sum, [, , cents]) => sum + Number(cents), 0);
}
JS
cat > report.test.mjs <<'JS'
const { default: assert } = await import('node:assert/strict');
const { readFileSync } = await import('node:fs');
const { default: test } = await import('node:test');
const { totalPaid } = await import('./report.mjs');
const csv = readFileSync(new URL('./orders.csv', import.meta.url), 'utf8');
test('only paid orders count', () => assert.equal(totalPaid(csv), 2000));
test('refunds alone count as zero', () => assert.equal(totalPaid('id,status,cents\nB,refunded,700\n'), 0));
test('an empty ledger counts as zero', () => assert.equal(totalPaid('id,status,cents\n'), 0));
JS
cp report.mjs report.original.mjs
node --test report.test.mjs
}
create_harness_lab

只檢查 orders.csv、report.mjs 和 report.test.mjs，先不要改檔案。說明測試要求的統計規則，指出已退款行，並執行 node --test report.test.mjs。解釋目前篩選為何得到 2700 而不是 2000。無法執行環境，請報告實際環境問題，不要編造輸出。

在這個一次性練習專案中修復 report.mjs，使 totalPaid 只統計 paid 行。先讀 orders.csv 和 report.test.mjs，執行 node --test report.test.mjs 並報告原始失敗。不要改 orders.csv、report.test.mjs 或 report.original.mjs；不要安裝依賴或存取其他目錄。以最小實作修改完成修復，重跑全部三項斷言，並根據 orders.csv 計算總額。最後列出修改檔案、實際測試結果、總額和限制。命令因環境原因失敗時，請與斷言失敗明確區分。

node --test report.test.mjs
node --input-type=module -e "import {readFileSync} from 'node:fs'; import {totalPaid} from './report.mjs'; console.log(totalPaid(readFileSync('orders.csv','utf8')))"
diff -u report.original.mjs report.mjs

.filter(([, status]) => status === 'paid')

create_cache_lab() {
test ! -e cache.mjs && test ! -e cache.test.mjs && test ! -e cache.original.mjs || return
cat > cache.mjs <<'JS'
let cached;
export function getSettings(config) {
  if (!cached || cached.account !== config.account) cached = { ...config };
  return cached;
}
JS
cat > cache.test.mjs <<'JS'
const { default: assert } = await import('node:assert/strict');
const { default: test } = await import('node:test');
const { getSettings } = await import('./cache.mjs');
test('a changed setting refreshes the instance', () => {
  const first = getSettings({ account: 'demo', mode: 'light' });
  const second = getSettings({ account: 'demo', mode: 'dark' });
  assert.notEqual(second, first);
  assert.equal(second.mode, 'dark');
  assert.equal(getSettings({ account: 'demo', mode: 'dark' }), second);
});
JS
cp cache.mjs cache.original.mjs
node --test cache.test.mjs
}
create_cache_lab

檢查 cache.mjs 和 cache.test.mjs，先重現失敗。修復快取，使 account 或 mode 任一變化都會建立新實例，相同值則重用已有實例。保留原測試；需要時單獨增加 account 變化斷言。不要引入依賴、定時器或全域清快取。執行 node --test cache.test.mjs，說明哪些輸入決定實例身份。

if (!cached || cached.account !== config.account || cached.mode !== config.mode) cached = { ...config };

為本練習寫 HANDOFF.md，包含目標、修改檔案、原始失敗、實際執行的精確命令及結果、剩餘問題（如有）和下一項驗證。不要包含認證資訊，不要聲稱通過尚未執行的檢查。新會話應能憑這份說明和目前檔案繼續。

cp report.mjs report.attempt.mjs
cp report.original.mjs report.mjs
node --test report.test.mjs