add: PostgreSQL 支持（asyncpg 驱动，from_url/from_config + 集成测试）

tests/test_database.py

@@ -0,0 +1,39 @@
+"""Database 构造与 from_config 的纯 API 校验（无 IO）。"""
+
+import pytest
+
+from chongming_database import Database
+
+
+async def test_constructor_requires_exactly_one_arg():
+    # 两个都不给
+    with pytest.raises(ValueError):
+        Database()
+    # 两个都给
+    with pytest.raises(ValueError):
+        Database("x.db", url="postgresql+asyncpg://localhost/db")
+
+
+async def test_from_config_sqlite_requires_path():
+    with pytest.raises(ValueError):
+        Database.from_config({"type": "sqlite"})
+
+
+async def test_from_config_postgres_requires_url():
+    with pytest.raises(ValueError):
+        Database.from_config({"type": "postgresql"})
+
+
+async def test_from_config_unsupported_type():
+    with pytest.raises(NotImplementedError):
+        Database.from_config({"type": "mysql", "url": "mysql://localhost/db"})
+
+
+async def test_postgres_url_normalized_to_asyncpg():
+    db = Database.from_url("postgresql://user:pwd@127.0.0.1:5432/mydb")
+    assert db._build_url() == "postgresql+asyncpg://user:pwd@127.0.0.1:5432/mydb"
+
+
+async def test_explicit_driver_url_untouched():
+    db = Database(url="postgresql+asyncpg://user:pwd@127.0.0.1:5432/mydb")
+    assert db._build_url() == "postgresql+asyncpg://user:pwd@127.0.0.1:5432/mydb"

tests/test_postgres.py

@@ -0,0 +1,74 @@
+"""PostgreSQL 后端集成测试（需 CHONGMING_TEST_PG_URL 环境变量，否则跳过）。"""
+
+import os
+import uuid
+
+import pytest
+from sqlmodel import Field, SQLModel, select
+
+from chongming_database import Database
+
+PG_URL = os.environ.get("CHONGMING_TEST_PG_URL")
+
+pytestmark = pytest.mark.skipif(
+    not PG_URL, reason="CHONGMING_TEST_PG_URL 未设置，跳过 PostgreSQL 集成测试"
+)
+
+
+def _make_item_table(tablename: str):
+    """动态生成随机表名的 SQLModel 表，避免污染共享 PG 实例。"""
+
+    class Item(SQLModel, table=True):
+        __tablename__ = tablename
+
+        id: int | None = Field(default=None, primary_key=True)
+        name: str = Field(max_length=50)
+
+    return Item
+
+
+async def test_postgres_crud():
+    Item = _make_item_table(f"pg_test_item_{uuid.uuid4().hex[:8]}")
+    db = Database.from_url(PG_URL)
+    await db.initialize()
+    try:
+        async with db.get_session() as session:
+            session.add(Item(name="pg"))
+            await session.commit()
+        async with db.get_session() as session:
+            rows = (await session.execute(select(Item))).scalars().all()
+            assert [r.name for r in rows] == ["pg"]
+    finally:
+        await db.dispose()
+
+
+async def test_postgres_bare_url_scheme():
+    """裸 postgresql:// 应被归一化为 postgresql+asyncpg:// 后正常连接。"""
+    bare = PG_URL.replace("postgresql+asyncpg://", "postgresql://", 1)
+    db = Database.from_url(bare)
+    await db.initialize()
+    try:
+        async with db.get_session() as session:
+            await session.execute(select(1))
+    finally:
+        await db.dispose()
+
+
+async def test_from_config_postgres_end_to_end():
+    db = Database.from_config({"type": "postgresql", "url": PG_URL})
+    await db.initialize()
+    try:
+        async with db.get_session() as session:
+            await session.execute(select(1))
+    finally:
+        await db.dispose()
+
+
+async def test_postgres_generate_schemas_false():
+    db = Database.from_url(PG_URL)
+    await db.initialize(generate_schemas=False)
+    try:
+        async with db.get_session() as session:
+            await session.execute(select(1))
+    finally:
+        await db.dispose()

tests/test_sqlite.py

@@ -0,0 +1,71 @@
+"""SQLite 后端回归测试（tmp_path，无需外部服务）。"""
+
+from pathlib import Path
+
+import pytest
+from sqlmodel import Field, SQLModel, select
+
+from chongming_database import Database
+
+
+class SqliteItem(SQLModel, table=True):
+    __tablename__ = "backend_test_item"
+
+    id: int | None = Field(default=None, primary_key=True)
+    name: str = Field(max_length=50)
+
+
+async def test_sqlite_crud(tmp_path: Path):
+    db = Database(tmp_path / "nested" / "test.db")
+    await db.initialize()
+    try:
+        async with db.get_session() as session:
+            session.add(SqliteItem(name="a"))
+            await session.commit()
+        async with db.get_session() as session:
+            rows = (await session.execute(select(SqliteItem))).scalars().all()
+            assert [r.name for r in rows] == ["a"]
+    finally:
+        await db.dispose()
+
+
+async def test_sqlite_initialize_is_idempotent(tmp_path: Path):
+    """重复 initialize（模拟多进程各自初始化）不应报错。"""
+    db = Database(tmp_path / "test.db")
+    await db.initialize()
+    try:
+        await db.initialize()
+    finally:
+        await db.dispose()
+
+
+async def test_get_session_before_initialize_raises(tmp_path: Path):
+    db = Database(tmp_path / "test.db")
+    try:
+        with pytest.raises(RuntimeError):
+            db.get_session()
+    finally:
+        await db.dispose()
+
+
+async def test_from_config_sqlite_end_to_end(tmp_path: Path):
+    db = Database.from_config(
+        {"type": "sqlite", "database_path": str(tmp_path / "cfg.db")}
+    )
+    await db.initialize()
+    try:
+        async with db.get_session() as session:
+            await session.execute(select(SqliteItem))
+    finally:
+        await db.dispose()
+
+
+async def test_generate_schemas_false_skips_ddl(tmp_path: Path):
+    """generate_schemas=False 时只建引擎不建表，会话仍可用。"""
+    db = Database(tmp_path / "noschema.db")
+    await db.initialize(generate_schemas=False)
+    try:
+        async with db.get_session() as session:
+            await session.execute(select(1))
+    finally:
+        await db.dispose()