test(core): cover DirHistory move-to-front, trim, persistence, bounds

[hi-neason]

Summary

core/dir_history.go tracks per-project recently-used directories (backing the /cd-style switch history). Its six exported methods carry non-trivial logic — move-to-front dedup on Add, trim-to-maxSize, 1-based indexing on Get with bounds checking, Previous fixed at index 2, defensive-copy on List, JSON persistence across instances — but the package had no dir_history_test.go. Existing coverage only instantiated NewDirHistory as setup in engine_test.go, so any regression in the history behavior itself would have gone unnoticed.

Change

No production code changes — this PR adds core/dir_history_test.go with 13 table-driven tests covering every exported method plus the load/reload and corrupt-file paths.

Type of change

• Internal refactor / chore (no user-visible change) — tests only

Testing

Automated tests added in this PR

core/dir_history_test.go:

• TestDirHistory_Add_MovesToFrontAndDedups — re-adding a directory moves it to the front and does not duplicate.
• TestDirHistory_Add_IgnoresEmpty — empty dir is a no-op.
• TestDirHistory_Add_TrimsToMaxSize — history is capped at the most recent N entries.
• TestDirHistory_SetMaxSize_AppliesToNextAdd — shrinking maxSize does not retroactively drop entries but trims on the next Add.
• TestDirHistory_SetMaxSize_ClampsToAtLeastOne — SetMaxSize(0) clamps to 1.
• TestDirHistory_Get_OneBasedAndBoundsCheck — index 1 is the most recent, index 0/out-of-range returns "".
• TestDirHistory_PreviousReturnsIndexTwo — Previous is hard-wired to the second-most-recent entry.
• TestDirHistory_Contains — true / false / unknown project cases.
• TestDirHistory_List_ReturnsDefensiveCopy — mutating the returned slice does not affect internal state.
• TestDirHistory_PerProjectIsolation — two projects do not share entries.
• TestDirHistory_PersistsAcrossInstances — a second NewDirHistory on the same data dir rehydrates from disk in most-recent-first order.
• TestDirHistory_Load_MissingFileIsNotAnError — empty data dir is not an error and List returns nil.
• TestDirHistory_Load_CorruptFileIsIgnored — malformed JSON is logged and ignored; subsequent Add still works.

For bug fixes only — regression test

Not applicable — test-only change with no production fix.

Critical User Journeys (CUJ) impact

• No CUJ touched (test-only change).

Manual / user-visible behavior change

None.

Checklist (reviewer will verify)

• go build ./... passes
• go test ./core/ -run TestDirHistory passes (all 13 new tests)
• AGENTS.md Pre-Commit Checklist items are satisfied
• No new hardcoded platform/agent names in core/
• No new i18n strings
• No secrets / credentials in source

Related

None.

[chenhg5]

结论: Approve

总体判断: 一个 test-only PR，给 core/dir_history.go 加了 13 个 table-driven 测试，覆盖 6 个 exported method + load/reload/corrupt 三个错误路径。production 代码不动，CI 全绿。建议合入。

Review 范围:

• 看了 core/dir_history_test.go 新增的 181 行 + 13 个测试函数。
• 看了 PR body 列出的覆盖矩阵（move-to-front / dedup / trim / bounds / persistence / corrupt / per-project isolation）。
• CI: run 31349356164 全绿。

✅ 做得好的地方:

• 覆盖矩阵完整：每个 exported method 都有独立测试，且覆盖 happy path + edge case + error path（corrupt JSON → ignored + 后续 Add 仍可用）。这种「不漏测」是后续 refactor dir_history.go 的安全网。
• Defensive copy 测试钉住不变式：TestDirHistory_List_ReturnsDefensiveCopy 验证 List 返回的 slice 修改不影响内部 state——这是 LRU-like 结构的常见 bug，作者明确测了它。
• Per-project isolation 测试：TestDirHistory_PerProjectIsolation 验证两个 project 不共享 entries。这是 data-structure correctness 的关键不变式，漏了会导致跨用户串数据。
• Persistence 测试用真实 filesystem：用 t.TempDir() + 第二次 NewDirHistory 实例化——不 mock filesystem 是合理选择（这是 stdlib JSON + 真实目录读写）。
• Corrupt JSON 测试钉住 graceful degradation：malformed JSON 时不 panic、log 但忽略、Add 仍工作。这是「用户数据损坏 → 不阻断服务」的标准 pattern。

🟠 建议改进（不阻塞）:

• TestDirHistory_PreviousReturnsIndexTwo 测试命名：实际钉住的是「Previous 固定返回 index 2」。如果未来 Previous 的语义被改成「上一条」（LRU 语义）而不是「倒数第二条」（固定的 index 2），这个测试需要跟着改。建议测试名更直接：TestDirHistory_PreviousReturnsSecondMostRecent 或加注释明确「previous = history index 2」的设计意图。
• TestDirHistory_Add_TrimsToMaxSize 没测「SetMaxSize 后再 trim」：作者写了 SetMaxSize_AppliesToNextAdd 但没明确「先 Add 5 个（maxSize=10）→ SetMaxSize(3) → Add 第 6 个 → 验证总长仍 10 但顺序不变」。建议补一个 case。
• Test 命名风格统一：13 个测试里有些用 TestDirHistory_Add_MovesToFrontAndDedups（方法_行为），有些用 TestDirHistory_PerProjectIsolation（行为）。建议统一为 Method_Behavior 风格便于 grep。

🔵 可选优化:

• 可以加一个 fuzz test（FuzzDirHistory_Add）验证任意输入序列都不 panic。低优先。

Testing / Risk:

• 已看到的验证: CI 全绿；13 个新测试通过。
• Blast radius: 0（test-only，无 production 改动）。

Next step:

• 建议 owner 直接 merge。Test-only PR，没有 production 改动风险，coverage 提升明显。