diff --git a/.gitignore b/.gitignore
index 862b977..3e88670 100644
--- a/.gitignore
+++ b/.gitignore
@@ -69,6 +69,8 @@ Thumbs.db
 # Project specific
 *.log
 data/
+!tests/data/
+!docs/data/
 logs/
 *.db
 *.sqlite
diff --git a/tests/data/test_backfill_15min_hardening.py b/tests/data/test_backfill_15min_hardening.py
new file mode 100644
index 0000000..af17c62
--- /dev/null
+++ b/tests/data/test_backfill_15min_hardening.py
@@ -0,0 +1,234 @@
+"""
+硬化测试：backfill_15min_baostock.py 三个硬伤的回归覆盖。
+
+覆盖：
+  1. 异常时强制重登（_relogin 在 backfill_one 重试 loop 中被调用）
+  2. 断路器（连续 N 失败 → break + sys.exit(2)）
+  3. marker-based resume（load_progress 从 marker 文件构造 done_set）
+  4. _login_with_timeout SIGALRM 超时（防 bs.login 永久挂起）
+
+mock baostock，不发起真实连接。
+"""
+
+import os
+import sys
+import tempfile
+import time
+from pathlib import Path
+
+import pandas as pd
+import pytest
+
+# 在 import backfill 模块前重定向 STOCK_ROOT，避免 setup_logging() 写入 NAS 挂载点
+_ROOT = Path(__file__).resolve().parents[2]
+if str(_ROOT) not in sys.path:
+    sys.path.insert(0, str(_ROOT))
+_FAKE_ROOT = tempfile.mkdtemp(prefix="backfill_test_")
+os.environ["STOCK_ROOT"] = _FAKE_ROOT
+
+import scripts.data_platform.backfill_15min_baostock as bf  # noqa: E402
+
+
+# ======================== fixture ========================
+
+@pytest.fixture
+def fake_df():
+    """一份合法的 15min DataFrame，够 backfill_one 写盘"""
+    return pd.DataFrame({
+        "day": ["2024-01-02 09:45:00", "2024-01-02 10:00:00"],
+        "open": [10.0, 10.2], "high": [10.3, 10.4],
+        "low": [9.9, 10.1], "close": [10.2, 10.3],
+        "volume": ["1000", "1200"], "amount": ["10000", "12000"],
+    })
+
+
+# ======================== 1. 异常时强制重登 ========================
+
+def test_relogin_called_on_exception(tmp_path, monkeypatch, fake_df):
+    """
+    fetch_bs_15min 第一次抛 socket 异常 →
+    backfill_one 重试 loop 应调 _relogin() 强制重登（新 socket）→
+    第二次 fetch 成功 → status=ok。
+    """
+    calls = {"fetch": 0, "relogin": 0}
+
+    def mock_fetch(bs_code, start_date, end_date):
+        calls["fetch"] += 1
+        if calls["fetch"] == 1:
+            raise OSError(57, "Socket is not connected")  # 模拟 baostock 断连
+        return fake_df
+
+    def mock_relogin():
+        calls["relogin"] += 1
+        return True
+
+    monkeypatch.setattr(bf, "MINUTE_15_DIR", tmp_path)
+    monkeypatch.setattr(bf, "fetch_bs_15min", mock_fetch)
+    monkeypatch.setattr(bf, "_relogin", mock_relogin)
+    monkeypatch.setattr(bf, "is_backfilled", lambda p: False)
+
+    status, rows = bf.backfill_one("000001", "2024-01-01", "2026-01-01", force=True)
+
+    assert status == "ok"
+    assert rows == 2
+    assert calls["fetch"] == 2          # 重试了一次
+    assert calls["relogin"] == 1        # 异常分支强制重登一次
+
+
+def test_relogin_failure_aborts_retry(tmp_path, monkeypatch):
+    """
+    异常 + _relogin 返回 False → 直接放弃，不再空转重试。
+    """
+    fetch_calls = {"n": 0}
+
+    def mock_fetch(*args, **kwargs):
+        fetch_calls["n"] += 1
+        raise OSError(57, "Socket is not connected")
+
+    monkeypatch.setattr(bf, "MINUTE_15_DIR", tmp_path)
+    monkeypatch.setattr(bf, "fetch_bs_15min", mock_fetch)
+    monkeypatch.setattr(bf, "_relogin", lambda: False)
+    monkeypatch.setattr(bf, "is_backfilled", lambda p: False)
+
+    status, rows = bf.backfill_one("000001", "2024-01-01", "2026-01-01", force=True)
+
+    assert status == "failed"
+    # _relogin 失败立即 break：fetch 只被调用 1 次（不会重试到 BS_MAX_RETRIES）
+    assert fetch_calls["n"] == 1
+
+
+# ======================== 2. 断路器 ========================
+
+def test_circuit_breaker_triggers(monkeypatch, tmp_path):
+    """
+    主循环连续 N 只 failed → 断路器触发，sys.exit(2)。
+    不真实登录 baostock、不读 CSV。
+    """
+    # 缩小阈值，加快测试
+    monkeypatch.setattr(bf, "CIRCUIT_BREAKER_THRESHOLD", 3)
+    # 所有桩
+    monkeypatch.setattr(bf, "NAS_ROOT", tmp_path)                # NAS_ROOT.exists() 通过
+    monkeypatch.setattr(bf, "MINUTE_15_DIR", tmp_path / "15min")
+    monkeypatch.setattr(bf, "_login_with_timeout", lambda timeout=30: True)
+    monkeypatch.setattr(bf, "_relogin", lambda: True)
+    monkeypatch.setattr(bf, "bs", type("S", (), {
+        "logout": staticmethod(lambda: None),
+        "login": staticmethod(lambda: type("L", (), {"error_code": "0", "error_msg": ""})()),
+    }))
+    monkeypatch.setattr(bf, "backfill_one", lambda *a, **k: ("failed", 0))
+    monkeypatch.setattr(bf, "save_progress", lambda s: None)
+    monkeypatch.setattr(bf, "time", type("T", (), {
+        "sleep": staticmethod(lambda s: None),
+        "time": staticmethod(time.time),
+    }))
+    # argv：5 个 fake 代码，触发阈值 3 后应中途 break
+    monkeypatch.setattr(sys, "argv", [
+        "backfill_15min_baostock.py",
+        "--codes", "000001,000002,000003,000004,000005",
+    ])
+
+    with pytest.raises(SystemExit) as exc_info:
+        bf.main()
+
+    assert exc_info.value.code == 2, "断路器触发应以退出码 2 退出"
+
+
+def test_circuit_breaker_resets_on_ok(monkeypatch, tmp_path):
+    """
+    ok 重置连续失败计数：N-1 失败后 1 个 ok，再 N-1 失败 → 不应触发断路。
+    最终正常退出（无 SystemExit）。
+    """
+    monkeypatch.setattr(bf, "CIRCUIT_BREAKER_THRESHOLD", 3)
+    monkeypatch.setattr(bf, "NAS_ROOT", tmp_path)
+    monkeypatch.setattr(bf, "MINUTE_15_DIR", tmp_path / "15min")
+    monkeypatch.setattr(bf, "_login_with_timeout", lambda timeout=30: True)
+    monkeypatch.setattr(bf, "_relogin", lambda: True)
+    monkeypatch.setattr(bf, "bs", type("S", (), {
+        "logout": staticmethod(lambda: None),
+        "login": staticmethod(lambda: type("L", (), {"error_code": "0", "error_msg": ""})()),
+    }))
+    # 序列：fail, fail, ok, fail, fail → 连续计数峰 2 < 3，不触发
+    seq = [("failed", 0), ("failed", 0), ("ok", 1), ("failed", 0), ("failed", 0)]
+    monkeypatch.setattr(bf, "backfill_one", lambda *a, **k: seq.pop(0))
+    monkeypatch.setattr(bf, "save_progress", lambda s: None)
+    monkeypatch.setattr(bf, "time", type("T", (), {
+        "sleep": staticmethod(lambda s: None),
+        "time": staticmethod(time.time),
+    }))
+    monkeypatch.setattr(sys, "argv", [
+        "backfill_15min_baostock.py",
+        "--codes", "000001,000002,000003,000004,000005",
+    ])
+
+    # 正常跑完不应抛 SystemExit
+    bf.main()
+
+
+# ======================== 3. marker-based resume ========================
+
+def test_load_progress_from_markers(tmp_path, monkeypatch):
+    """
+    load_progress 从 .{prefix}{code}_15min.baostock marker 构造 done_set。
+    failed 票无 marker → 不在 done_set → 下次复跑会被重试。
+    """
+    monkeypatch.setattr(bf, "MINUTE_15_DIR", tmp_path)
+
+    # 成功票：写 marker
+    for name in [".sh600000_15min.baostock", ".sz000001_15min.baostock",
+                 ".sh688981_15min.baostock"]:
+        (tmp_path / name).write_text("2026-07-13T00:00:00")
+    # 失败票：只有 parquet，无 marker（不应进 done_set）
+    (tmp_path / "sz300750_15min.parquet").write_text("dummy")
+    # 无关文件
+    (tmp_path / ". unrelated.baostock").write_text("x")
+    (tmp_path / ".sh600000_daily.baostock").write_text("x")  # 非 _15min
+
+    done = bf.load_progress()
+
+    assert done == {"600000", "000001", "688981"}
+    assert "300750" not in done     # failed（无 marker）会被重试
+
+
+def test_load_progress_empty_when_dir_missing(tmp_path, monkeypatch):
+    """目录不存在 → 空集合（不抛异常）"""
+    monkeypatch.setattr(bf, "MINUTE_15_DIR", tmp_path / "nonexistent")
+    assert bf.load_progress() == set()
+
+
+# ======================== 4. login 超时 ========================
+
+def test_login_with_timeout_fires(monkeypatch):
+    """
+    bs.login() 卡死（sleep 远大于 timeout）→ SIGALRM 触发 → 返回 False。
+    验证不会永久挂起。
+    """
+    def slow_login():
+        time.sleep(10)  # 模拟 baostock 卡死
+        return type("L", (), {"error_code": "0", "error_msg": ""})()
+
+    monkeypatch.setattr(bf, "bs", type("S", (), {"login": staticmethod(slow_login)}))
+
+    t0 = time.time()
+    ok = bf._login_with_timeout(timeout=1)
+    elapsed = time.time() - t0
+
+    assert ok is False
+    assert elapsed < 3, f"超时应快速返回，实际 {elapsed:.1f}s"
+
+
+def test_login_with_timeout_success(monkeypatch):
+    """正常登录 → 返回 True"""
+    def quick_login():
+        return type("L", (), {"error_code": "0", "error_msg": ""})()
+
+    monkeypatch.setattr(bf, "bs", type("S", (), {"login": staticmethod(quick_login)}))
+    assert bf._login_with_timeout(timeout=5) is True
+
+
+def test_login_with_timeout_login_failure(monkeypatch):
+    """baostock 返回 error_code != 0 → 返回 False"""
+    def fail_login():
+        return type("L", (), {"error_code": "10001", "error_msg": "网络断开"})()
+
+    monkeypatch.setattr(bf, "bs", type("S", (), {"login": staticmethod(fail_login)}))
+    assert bf._login_with_timeout(timeout=5) is False