Initial commit: email-openclaw bridge v1

Full pipeline: IMAP ingress -> OpenClaw dispatch -> callback -> SMTP reply.
SQLite stateful storage with idempotency, threading, and retry logic.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

checkpoints/006-tests.md

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+# Checkpoint 006 — Tests
+
+**Ngày:** 2026-04-24  
+**Trạng thái:** ✅ Hoàn thành  
+**Verify:** `go test ./... -v` — 10/10 PASS
+
+---
+
+## Test matrix coverage
+
+| # | Scenario | Test | Status |
+|---|----------|------|--------|
+| 1 | Callback hợp lệ → CALLBACK_DONE | `TestCallback_ValidToken_UpdatesTask` | ✅ PASS |
+| 2 | OpenClaw fail 2 lần, lần 3 OK → attempt=3 | `TestDispatch_RetryThenSuccess` | ✅ PASS |
+| 2' | OpenClaw fail hết → FAILED + last_error | `TestDispatch_AllRetriesFailed` | ✅ PASS |
+| 3 | SMTP fail hết retry → FAILED | *(cần SMTP mock — chưa test)* | ⏳ |
+| 4 | Callback sai token → 401, state không đổi | `TestCallback_WrongToken_Returns401` | ✅ PASS |
+| 5 | Duplicate message_id → không tạo task mới | `TestDuplicateMessageID` | ✅ PASS |
+| 6 | Anti-loop / whitelist → IGNORED | *(logic test trong IMAP — chưa test)* | ⏳ |
+
+**Bonus tests:**
+- `TestCallback_AlreadyCompleted_Idempotent` — idempotent callback ✅
+- `TestFindByMessageID_NotFound` — empty result handling ✅
+- `TestThreadHistory` — chỉ trả COMPLETED tasks ✅
+- `TestHealthz`, `TestReadyz` — health endpoints ✅
+
+## Kỹ thuật test
+
+- **Test database:** `database.NewTestDB(t)` tạo SQLite tạm trong `t.TempDir()`
+- **HTTP mock:** `httptest.NewServer` cho OpenClaw API
+- **HTTP test:** `httptest.NewServer(router)` cho callback handler
+- **Retry timing:** Tests thật sự chờ backoff (1s+5s = ~6s mỗi retry test)
+
+## Files mới
+
+- `internal/database/testhelper.go` — TestDB helper
+- `internal/database/repository_test.go` — repository tests
+- `internal/api/router_test.go` — callback + health tests
+- `internal/ai_client/client_test.go` — dispatch retry tests
+
+## Chưa test (cần mock phức tạp hơn)
+
+- SMTP retry logic (#3) — cần mock `net/smtp.SendMail`
+- IMAP anti-loop/whitelist (#6) — cần refactor `processMessage` để testable