DeepSeek Harness 最佳实践：完成两个可核验的修复

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

只检查 orders.csv、report.mjs 和 report.test.mjs，先不要改文件。说明测试要求的统计规则，指出已退款行，并执行 node --test report.test.mjs。解释当前筛选为何得到 2700 而不是 2000。无法运行时，请报告实际环境问题，不要编造输出。

在这个一次性练习项目中修复 report.mjs，使 totalPaid 只统计 paid 行。先读 orders.csv 和 report.test.mjs，执行 node --test report.test.mjs 并报告原始失败。不要改 orders.csv、report.test.mjs 或 report.original.mjs；不要安装依赖或访问其他目录。以最小实现修改完成修复，重跑全部三项断言，并根据 orders.csv 计算总额。最后列出修改文件、实际测试结果、总额和局限。命令因环境原因失败时，请与断言失败明确区分。

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

检查 cache.mjs 和 cache.test.mjs，先复现失败。修复缓存，使 account 或 mode 任一变化都会构造新实例，相同值则复用已有实例。保留原测试；需要时单独增加 account 变化断言。不要引入依赖、定时器或全局清缓存。运行 node --test cache.test.mjs，说明哪些输入决定实例身份。

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

为本练习写 HANDOFF.md，包含目标、修改文件、原始失败、实际执行的精确命令及结果、剩余问题（如有）和下一项验证。不要包含凭据，不要声称通过尚未执行的检查。新会话应能凭这份说明和当前文件继续。

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