diff --git a/tests/unit/test_asset_libraries_use_case.py b/tests/unit/test_asset_libraries_use_case.py
new file mode 100755
index 000000000..6493a5061
--- /dev/null
+++ b/tests/unit/test_asset_libraries_use_case.py
@@ -0,0 +1,157 @@
+"""素材库 UseCase 单元测试."""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from packages.application.asset_libraries import (
+    CreateAssetLibraryCommand,
+    CreateAssetLibraryUseCase,
+    ListAssetLibrariesUseCase,
+)
+from packages.domain import AssetLibrary, AssetLibraryKind
+
+
+@pytest.fixture
+def mock_repo():
+    repo = MagicMock()
+    return repo
+
+
+@pytest.fixture
+def sample_library():
+    lib = AssetLibrary.create(
+        project_id="proj_456",
+        name="测试视频库",
+        kind=AssetLibraryKind.VIDEO,
+    )
+    lib.id = "lib_123"
+    return lib
+
+
+class TestListAssetLibrariesUseCase:
+    """ListAssetLibrariesUseCase 测试"""
+
+    def test_list_returns_repo_results(self, mock_repo, sample_library):
+        """正常返回 repository 的查询结果"""
+        mock_repo.find_by_project.return_value = [sample_library]
+        use_case = ListAssetLibrariesUseCase(mock_repo)
+
+        result = use_case.execute("proj_456")
+
+        assert len(result) == 1
+        assert result[0].id == "lib_123"
+        mock_repo.find_by_project.assert_called_once_with("proj_456")
+
+    def test_empty_project_raises_value_error(self, mock_repo):
+        """空 project_id 抛出 ValueError"""
+        use_case = ListAssetLibrariesUseCase(mock_repo)
+
+        with pytest.raises(ValueError, match="project_id 不能为空"):
+            use_case.execute("")
+
+        mock_repo.find_by_project.assert_not_called()
+
+    def test_whitespace_project_raises_value_error(self, mock_repo):
+        """纯空格 project_id 也抛出 ValueError"""
+        use_case = ListAssetLibrariesUseCase(mock_repo)
+
+        with pytest.raises(ValueError, match="project_id 不能为空"):
+            use_case.execute("   ")
+
+        mock_repo.find_by_project.assert_not_called()
+
+    def test_project_id_stripped_before_query(self, mock_repo, sample_library):
+        """project_id 会被 strip 后再查询"""
+        mock_repo.find_by_project.return_value = [sample_library]
+        use_case = ListAssetLibrariesUseCase(mock_repo)
+
+        use_case.execute("  proj_456  ")
+
+        mock_repo.find_by_project.assert_called_once_with("proj_456")
+
+    def test_empty_list(self, mock_repo):
+        """项目没有素材库时返回空列表"""
+        mock_repo.find_by_project.return_value = []
+        use_case = ListAssetLibrariesUseCase(mock_repo)
+
+        result = use_case.execute("proj_456")
+
+        assert result == []
+
+
+class TestCreateAssetLibraryUseCase:
+    """CreateAssetLibraryUseCase 测试"""
+
+    def test_create_success(self, mock_repo, sample_library):
+        """创建成功返回 AssetLibrary"""
+        mock_repo.create.return_value = sample_library
+        use_case = CreateAssetLibraryUseCase(mock_repo)
+
+        command = CreateAssetLibraryCommand(
+            project_id="proj_456",
+            name="新素材库",
+            kind=AssetLibraryKind.IMAGE,
+        )
+        result = use_case.execute(command)
+
+        assert result.id == "lib_123"
+        mock_repo.create.assert_called_once()
+        # 验证传入 repository 的是一个 AssetLibrary 对象
+        created = mock_repo.create.call_args[0][0]
+        assert isinstance(created, AssetLibrary)
+        assert created.project_id == "proj_456"
+        assert created.name == "新素材库"
+        assert created.kind == AssetLibraryKind.IMAGE
+
+    def test_create_with_video_kind(self, mock_repo):
+        """创建视频类型素材库"""
+        mock_repo.create.side_effect = lambda x: x
+        use_case = CreateAssetLibraryUseCase(mock_repo)
+
+        command = CreateAssetLibraryCommand(
+            project_id="proj_1",
+            name="视频库",
+            kind=AssetLibraryKind.VIDEO,
+        )
+        result = use_case.execute(command)
+
+        assert result.kind == AssetLibraryKind.VIDEO
+        assert result.name == "视频库"
+
+    def test_create_with_voice_kind(self, mock_repo):
+        """创建音色类型素材库"""
+        mock_repo.create.side_effect = lambda x: x
+        use_case = CreateAssetLibraryUseCase(mock_repo)
+
+        command = CreateAssetLibraryCommand(
+            project_id="proj_1",
+            name="音色库",
+            kind=AssetLibraryKind.VOICE,
+        )
+        result = use_case.execute(command)
+
+        assert result.kind == AssetLibraryKind.VOICE
+
+
+class TestCreateAssetLibraryCommand:
+    """CreateAssetLibraryCommand 数据类测试"""
+
+    def test_command_fields(self):
+        """命令对象字段正确"""
+        cmd = CreateAssetLibraryCommand(
+            project_id="proj_1",
+            name="test",
+            kind=AssetLibraryKind.VIDEO,
+        )
+        assert cmd.project_id == "proj_1"
+        assert cmd.name == "test"
+        assert cmd.kind == AssetLibraryKind.VIDEO
+
+    def test_command_is_dataclass(self):
+        """命令是 dataclass"""
+        from dataclasses import is_dataclass
+
+        assert is_dataclass(CreateAssetLibraryCommand)
diff --git a/tests/unit/test_bgm_utils.py b/tests/unit/test_bgm_utils.py
new file mode 100755
index 000000000..523a8331a
--- /dev/null
+++ b/tests/unit/test_bgm_utils.py
@@ -0,0 +1,105 @@
+"""BGM 配置工具函数单元测试."""
+
+import pytest
+
+from packages.domain.bgm_utils import merge_bgm_config
+
+
+class TestMergeBgmConfig:
+    """merge_bgm_config 测试"""
+
+    def test_user_bgm_empty_returns_template_copy(self):
+        """用户配置为空时，返回模板配置的拷贝"""
+        template = {"enabled": True, "volume": 0.5, "asset_id": "tpl_123"}
+        result = merge_bgm_config(template, {})
+        assert result == template
+        assert result is not template
+
+    def test_user_bgm_none_returns_template_copy(self):
+        """用户配置为 None 时，返回模板配置的拷贝"""
+        template = {"enabled": True, "volume": 0.5}
+        result = merge_bgm_config(template, None)  # type: ignore
+        assert result == template
+
+    def test_template_bgm_empty_returns_user_copy(self):
+        """模板配置为空时，返回用户配置的拷贝"""
+        user = {"enabled": False, "volume": 0.8, "asset_id": "user_456"}
+        result = merge_bgm_config({}, user)
+        assert result == user
+        assert result is not user
+
+    def test_template_bgm_none_returns_user_copy(self):
+        """模板配置为 None 时，返回用户配置的拷贝"""
+        user = {"enabled": False, "volume": 0.8}
+        result = merge_bgm_config(None, user)  # type: ignore
+        assert result == user
+
+    def test_user_fields_override_template(self):
+        """用户显式指定的字段覆盖模板对应字段"""
+        template = {
+            "enabled": True,
+            "volume": 0.5,
+            "asset_id": "tpl_123",
+            "fade_in": 1.0,
+        }
+        user = {
+            "volume": 0.8,
+            "asset_id": "user_456",
+        }
+        result = merge_bgm_config(template, user)
+        assert result["volume"] == 0.8
+        assert result["asset_id"] == "user_456"
+        assert result["fade_in"] == 1.0  # 模板值保留
+
+    def test_enabled_not_in_user_preserves_template_enabled(self):
+        """enabled 特殊处理：用户没传 enabled 时保留模板的 enabled 值"""
+        template = {"enabled": True, "volume": 0.5}
+        user = {"volume": 0.8}  # 没传 enabled
+        result = merge_bgm_config(template, user)
+        assert result["enabled"] is True  # 保留模板的
+        assert result["volume"] == 0.8  # 用户指定的覆盖
+
+    def test_enabled_in_user_overrides_template(self):
+        """用户传了 enabled 时覆盖模板的 enabled"""
+        template = {"enabled": True, "volume": 0.5}
+        user = {"enabled": False, "volume": 0.8}
+        result = merge_bgm_config(template, user)
+        assert result["enabled"] is False
+        assert result["volume"] == 0.8
+
+    def test_user_adds_new_fields(self):
+        """用户配置中的新字段会被添加到结果中"""
+        template = {"enabled": True, "volume": 0.5}
+        user = {"sidechain_enabled": True, "sidechain_ratio": 0.6}
+        result = merge_bgm_config(template, user)
+        assert result["enabled"] is True
+        assert result["volume"] == 0.5
+        assert result["sidechain_enabled"] is True
+        assert result["sidechain_ratio"] == 0.6
+
+    def test_both_empty_returns_empty_dict(self):
+        """两者都为空时返回空字典"""
+        result = merge_bgm_config({}, {})
+        assert result == {}
+
+    def test_nested_dict_shallow_merge(self):
+        """嵌套字典是浅合并（当前设计）"""
+        template = {"enabled": True, "config": {"eq": True, "compression": False}}
+        user = {"config": {"compression": True, "reverb": 0.5}}
+        result = merge_bgm_config(template, user)
+        # 浅合并：整个 config 被用户值覆盖
+        assert result["config"] == {"compression": True, "reverb": 0.5}
+
+    def test_does_not_mutate_template(self):
+        """不修改原始模板配置"""
+        template = {"enabled": True, "volume": 0.5}
+        original = dict(template)
+        merge_bgm_config(template, {"volume": 0.8})
+        assert template == original
+
+    def test_does_not_mutate_user(self):
+        """不修改原始用户配置"""
+        user = {"volume": 0.8}
+        original = dict(user)
+        merge_bgm_config({"enabled": True}, user)
+        assert user == original
diff --git a/tests/unit/test_domain_exceptions.py b/tests/unit/test_domain_exceptions.py
new file mode 100755
index 000000000..7318a4df9
--- /dev/null
+++ b/tests/unit/test_domain_exceptions.py
@@ -0,0 +1,131 @@
+"""领域层通用异常单元测试."""
+
+import pytest
+
+from packages.domain.exceptions import (
+    DomainError,
+    NotFoundError,
+    QuotaExceededError,
+    ValidationError,
+)
+
+
+class TestDomainError:
+    """DomainError 基类测试"""
+
+    def test_is_exception(self):
+        """DomainError 是 Exception 的子类"""
+        assert issubclass(DomainError, Exception)
+
+    def test_can_raise_and_catch(self):
+        """可以抛出和捕获"""
+        with pytest.raises(DomainError):
+            raise DomainError("something went wrong")
+
+    def test_message(self):
+        """异常消息正确"""
+        err = DomainError("test message")
+        assert str(err) == "test message"
+
+
+class TestNotFoundError:
+    """NotFoundError 测试"""
+
+    def test_is_domain_error(self):
+        """NotFoundError 继承自 DomainError"""
+        assert issubclass(NotFoundError, DomainError)
+
+    def test_can_raise_as_domain_error(self):
+        """可以作为 DomainError 捕获"""
+        with pytest.raises(DomainError):
+            raise NotFoundError("resource not found")
+
+    def test_default_message(self):
+        """无参构造"""
+        err = NotFoundError()
+        assert isinstance(err, NotFoundError)
+
+    def test_custom_message(self):
+        """自定义消息"""
+        err = NotFoundError("user 123 not found")
+        assert str(err) == "user 123 not found"
+
+
+class TestValidationError:
+    """ValidationError 测试"""
+
+    def test_is_domain_error(self):
+        """ValidationError 继承自 DomainError"""
+        assert issubclass(ValidationError, DomainError)
+
+    def test_can_raise_as_domain_error(self):
+        """可以作为 DomainError 捕获"""
+        with pytest.raises(DomainError):
+            raise ValidationError("invalid input")
+
+    def test_custom_message(self):
+        """自定义消息"""
+        err = ValidationError("duration must be positive")
+        assert str(err) == "duration must be positive"
+
+
+class TestQuotaExceededError:
+    """QuotaExceededError 测试"""
+
+    def test_is_domain_error(self):
+        """QuotaExceededError 继承自 DomainError"""
+        assert issubclass(QuotaExceededError, DomainError)
+
+    def test_can_raise_as_domain_error(self):
+        """可以作为 DomainError 捕获"""
+        with pytest.raises(DomainError):
+            raise QuotaExceededError("storage", 1024.0, 2048.0)
+
+    def test_stores_dimension_limit_used(self):
+        """保存 dimension、limit、used 属性"""
+        err = QuotaExceededError("storage_mb", 1024.0, 1500.0)
+        assert err.dimension == "storage_mb"
+        assert err.limit == 1024.0
+        assert err.used == 1500.0
+
+    def test_error_message_format(self):
+        """异常消息格式正确"""
+        err = QuotaExceededError("storage_mb", 1024.0, 1500.0)
+        msg = str(err)
+        assert "storage_mb" in msg
+        assert "1500.0" in msg
+        assert "1024.0" in msg
+        assert "Quota exceeded" in msg
+
+    def test_integer_values(self):
+        """整数值也能正常工作"""
+        err = QuotaExceededError("projects", 10, 15)
+        assert err.dimension == "projects"
+        assert err.limit == 10
+        assert err.used == 15
+
+    def test_zero_limit(self):
+        """限制为 0 时也能正常工作"""
+        err = QuotaExceededError("custom_templates", 0, 1)
+        assert err.limit == 0
+        assert err.used == 1
+
+
+class TestExceptionHierarchy:
+    """异常继承关系测试"""
+
+    def test_all_are_domain_errors(self):
+        """所有异常都可以作为 DomainError 捕获"""
+        errors = [
+            NotFoundError(),
+            ValidationError("bad"),
+            QuotaExceededError("x", 10.0, 20.0),
+        ]
+        for err in errors:
+            assert isinstance(err, DomainError)
+
+    def test_distinct_types(self):
+        """不同异常类型可以区分"""
+        assert not issubclass(NotFoundError, ValidationError)
+        assert not issubclass(ValidationError, QuotaExceededError)
+        assert not issubclass(NotFoundError, QuotaExceededError)