CI: rewrite session-fixture med transaction rollback og dedikeret connection

backend/tests/conftest.py

@@ -2,7 +2,10 @@
 
 import pytest
 import pytest_asyncio
-from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker
+from sqlalchemy.ext.asyncio import (
+    create_async_engine,
+    async_sessionmaker,
+)
 from httpx import ASGITransport, AsyncClient
 
 from app.database import Base, get_db
@@ -33,10 +36,23 @@ async def engine():
 
 @pytest_asyncio.fixture
 async def session(engine):
-    """Per-test database session."""
-    maker = async_sessionmaker(engine, expire_on_commit=False)
+    """Per-test database session med transaction rollback.
+
+    Hver test får sin egen connection med en ydre transaction.
+    commit() inde i testen opretter en savepoint (via create_savepoint),
+    så al data rulles tilbage efter testen — ingen krydskontaminering.
+    """
+    conn = await engine.connect()
+    transaction = await conn.begin()
+    maker = async_sessionmaker(
+        bind=conn,
+        expire_on_commit=False,
+        join_transaction_mode="create_savepoint",
+    )
     async with maker() as s:
         yield s
+    await transaction.rollback()
+    await conn.close()
 
 
 @pytest_asyncio.fixture
@@ -55,7 +71,7 @@ async def client(session):
 
 @pytest_asyncio.fixture
 async def admin_user(session):
-    """Insert admin user into test DB."""
+    """Insert admin user into test DB (rulles tilbage af session-fixture)."""
     u = User(
         username="admin",
         password_hash=hash_password("admin123"),
@@ -68,7 +84,7 @@ async def admin_user(session):
 
 @pytest_asyncio.fixture
 async def normal_user(session):
-    """Insert normal user into test DB."""
+    """Insert normal user into test DB (rulles tilbage af session-fixture)."""
     u = User(
         username="testuser",
         password_hash=hash_password("test123"),