diff --git a/common/pyproject.toml b/common/pyproject.toml
index 1a1068f..5f32862 100644
--- a/common/pyproject.toml
+++ b/common/pyproject.toml
@@ -31,3 +31,7 @@ default = true
 dev = [
     "pytest>=9.1.1",
 ]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+testpaths = ["tests"]
diff --git a/common/tests/__init__.py b/common/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/common/tests/storage/__init__.py b/common/tests/storage/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/common/tests/storage/test_factory.py b/common/tests/storage/test_factory.py
new file mode 100644
index 0000000..5c1079a
--- /dev/null
+++ b/common/tests/storage/test_factory.py
@@ -0,0 +1,134 @@
+"""create_storage 工厂测试：覆盖 mode 字段严格拒绝 + 正常路径。"""
+
+from common.storage.base import AsyncStorageBackend
+from common.storage.exceptions import StorageConfigError
+from common.storage.factory import (
+    PURPOSE_BUCKETS,
+    USAGE_TYPE_TO_PURPOSE,
+    build_storage_config,
+    create_storage,
+)
+
+
+# ── mode 字段严格拒绝 ──────────────────────────────────────────────
+
+
+def test_create_storage_rejects_mode_sync():
+    """显式 mode='sync' 现在必须拒绝 —— 同步抽象已砍掉。"""
+    import pytest
+
+    with pytest.raises(StorageConfigError) as exc_info:
+        create_storage({"type": "local", "base_dir": "/tmp", "mode": "sync"})
+    msg = str(exc_info.value)
+    assert "不再接受 'mode' 字段" in msg
+
+
+def test_create_storage_rejects_mode_async():
+    """显式 mode='async' 也必须拒绝 —— 只有 async 一条路，不需要再声明。"""
+    import pytest
+
+    with pytest.raises(StorageConfigError) as exc_info:
+        create_storage({"type": "s3", "bucket": "x", "mode": "async"})
+    msg = str(exc_info.value)
+    assert "不再接受 'mode' 字段" in msg
+
+
+def test_create_storage_rejects_any_mode_value():
+    """任何 mode 字段（包含未来可能新增的合法值）都拒绝 —— 简化语义。"""
+    import pytest
+
+    for value in ("async", "sync", "dual", ""):
+        with pytest.raises(StorageConfigError):
+            create_storage({"type": "local", "base_dir": "/tmp", "mode": value})
+
+
+# ── 正常路径 ────────────────────────────────────────────────────────
+
+
+def test_create_storage_returns_async_subclass():
+    s = create_storage({"type": "local", "base_dir": "/tmp/cc-factory-test"})
+    assert isinstance(s, AsyncStorageBackend)
+    # 确认是真 AsyncStorageBackend，不是同步兼容形态
+    assert type(s).__name__ == "LocalStorageBackend"
+
+
+def test_create_storage_missing_type_raises():
+    import pytest
+
+    with pytest.raises(StorageConfigError) as exc_info:
+        create_storage({"base_dir": "/tmp"})
+    assert "缺少 'type' 字段" in str(exc_info.value)
+
+
+def test_create_storage_unknown_type_raises():
+    import pytest
+
+    with pytest.raises(StorageConfigError) as exc_info:
+        create_storage({"type": "nonexistent"})
+    assert "未知的存储后端" in str(exc_info.value)
+
+
+def test_create_storage_does_not_mutate_input_dict():
+    """调用方传入的字典不能被改写。"""
+    cfg = {"type": "local", "base_dir": "/tmp/cc-no-mutate"}
+    cfg_id = id(cfg)
+    snapshot = dict(cfg)
+    create_storage(cfg)
+    assert dict(cfg) == snapshot, "factory should not mutate caller's dict"
+    assert id(cfg) == cfg_id
+
+
+def test_create_storage_kwargs_mismatch_raises_wrapped_error():
+    import pytest
+
+    with pytest.raises(StorageConfigError) as exc_info:
+        create_storage({"type": "local", "base_dir": 12345})  # base_dir 必须是 str
+    msg = str(exc_info.value)
+    assert "参数不匹配" in msg
+
+
+# ── build_storage_config 不再产生 mode 字段 ─────────────────────────
+
+
+def test_build_storage_config_local_has_no_mode(monkeypatch):
+    """local 分支的输出 dict 不能含 'mode'。"""
+    from common import config as common_config
+
+    monkeypatch.setattr(common_config.settings, "storage_backend", "local", raising=False)
+    monkeypatch.setattr(common_config.settings, "local_storage_base_dir", "/tmp", raising=False)
+
+    cfg = build_storage_config("workspace")
+    assert "mode" not in cfg, f"local cfg must not have 'mode', got: {cfg}"
+    assert cfg["type"] == "local"
+    assert "base_dir" in cfg
+
+
+def test_build_storage_config_s3_has_no_mode(monkeypatch):
+    """s3 分支的输出 dict 也不能含 'mode'。"""
+    from common import config as common_config
+
+    monkeypatch.setattr(common_config.settings, "storage_backend", "s3", raising=False)
+    monkeypatch.setattr(common_config.settings, "s3_workspace_bucket", "wb", raising=False)
+    monkeypatch.setattr(common_config.settings, "s3_endpoint", "http://s3", raising=False)
+    monkeypatch.setattr(common_config.settings, "s3_access_key", "ak", raising=False)
+    monkeypatch.setattr(common_config.settings, "s3_secret_key", "sk", raising=False)
+
+    cfg = build_storage_config("workspace")
+    assert "mode" not in cfg, f"s3 cfg must not have 'mode', got: {cfg}"
+    assert cfg["type"] == "s3"
+
+
+def test_build_storage_config_unknown_bucket_raises():
+    import pytest
+
+    from common.storage.exceptions import StorageConfigError
+    with pytest.raises(StorageConfigError):
+        build_storage_config("not-a-real-bucket")
+
+
+def test_purpose_buckets_constant_complete():
+    """PURPOSE_BUCKETS 必须覆盖 USAGE_TYPE_TO_PURPOSE 中所有 purpose。"""
+    purposes = set(USAGE_TYPE_TO_PURPOSE.values())
+    assert purposes.issubset(set(PURPOSE_BUCKETS)), (
+        f"missing buckets for purposes: {purposes - set(PURPOSE_BUCKETS)}"
+    )
\ No newline at end of file
diff --git a/common/tests/storage/test_registry.py b/common/tests/storage/test_registry.py
new file mode 100644
index 0000000..34be20a
--- /dev/null
+++ b/common/tests/storage/test_registry.py
@@ -0,0 +1,71 @@
+"""后端注册表测试：覆盖 register / get / 内置 backend 注册。"""
+
+from common.storage.base import AsyncStorageBackend
+from common.storage.exceptions import StorageConfigError
+from common.storage.registry import (
+    get_backend_class,
+    register_backend,
+    registered_backends,
+)
+
+
+def test_local_and_s3_are_registered_at_import_time():
+    """import common.storage 应该触发 local / s3 的注册。"""
+    backend_classes = registered_backends()
+    assert "local" in backend_classes
+    assert "s3" in backend_classes
+    for cls in backend_classes.values():
+        assert issubclass(cls, AsyncStorageBackend)
+
+
+def test_get_backend_class_returns_async_subclass():
+    cls = get_backend_class("local")
+    assert issubclass(cls, AsyncStorageBackend)
+
+
+def test_get_backend_class_unknown_raises():
+    import pytest
+
+    with pytest.raises(StorageConfigError) as exc_info:
+        get_backend_class("does-not-exist")
+    assert "未知的存储后端" in str(exc_info.value)
+    assert "does-not-exist" in str(exc_info.value)
+
+
+def test_register_backend_idempotent_for_same_class():
+    """同一个类对象重复注册是 no-op，不抛错（``is`` 比对，避免重复 import 时误冲突）。"""
+    from common.storage.registry import _REGISTRY
+
+    class _SameAgain(AsyncStorageBackend):
+        pass
+
+    _REGISTRY["same-again-test"] = _SameAgain
+
+    # 第二次装饰同一个类对象：当前实现里装饰器返回 cls 并把 _REGISTRY[name] 重新写一遍。
+    # 直接重新调用 register_backend("same-again-test")(_SameAgain) 不抛错即可。
+    fn = register_backend("same-again-test")
+    result = fn(_SameAgain)
+    assert result is _SameAgain
+    assert _REGISTRY["same-again-test"] is _SameAgain
+
+    _REGISTRY.pop("same-again-test", None)
+
+
+def test_register_backend_conflict_raises():
+    import pytest
+
+    @register_backend("conflict-test")
+    class A(AsyncStorageBackend):
+        pass
+
+    with pytest.raises(StorageConfigError) as exc_info:
+
+        @register_backend("conflict-test")
+        class B(AsyncStorageBackend):
+            pass
+
+    assert "已被注册" in str(exc_info.value)
+
+    # cleanup：避免污染全局 registry 影响其他测试
+    from common.storage.registry import _REGISTRY
+    _REGISTRY.pop("conflict-test", None)
\ No newline at end of file