test(conftest): add in_memory_db and task manager singleton reset fixtures; fix broken tests

- Replace conftest.py with two autouse fixtures: reset_graph_factory_singleton
  and reset_task_manager_singleton, plus in_memory_db fixture for tests
  requiring a real DB
- Rewrite test_project_task_recovery.py to use ProjectManager + SQLite in-memory
  DB instead of the removed Project dataclass (same guarantee: active_task_id
  persists and defaults to None)
- Fix db.py init_db() to import db_models before Base.metadata.create_all() so
  all ORM tables are registered and created on first startup

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/db.py

@@ -19,6 +19,8 @@ def init_db(database_url: str) -> None:
     connect_args = {"check_same_thread": False} if database_url.startswith("sqlite") else {}
     _engine = create_engine(database_url, connect_args=connect_args, echo=False)
     _SessionLocal = sessionmaker(bind=_engine, autocommit=False, autoflush=False)
+    # Import models so that all ORM classes register with Base.metadata before create_all
+    from .models import db_models as _  # noqa: F401
     Base.metadata.create_all(_engine)
 
 

backend/tests/conftest.py

@@ -1,12 +1,38 @@
+# backend/tests/conftest.py
 import pytest
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from backend.app.db import Base
+import backend.app.db as db_module
 
 
 @pytest.fixture(autouse=True)
 def reset_graph_factory_singleton():
-    """Reset the graph backend singleton before each test to avoid cross-test contamination."""
+    """Reset the graph backend singleton before each test."""
     yield
     try:
         import backend.app.graph.factory as fmod
         fmod._backend_instance = None
     except ImportError:
         pass
+
+
+@pytest.fixture(autouse=True)
+def reset_task_manager_singleton():
+    """Reset TaskManager singleton between tests."""
+    from backend.app.models import task as task_module
+    task_module.TaskManager._instance = None
+    yield
+    task_module.TaskManager._instance = None
+
+
+@pytest.fixture
+def in_memory_db():
+    """BD SQLite en memòria per a tests que necessiten BD."""
+    db_module._engine = create_engine("sqlite:///:memory:", connect_args={"check_same_thread": False})
+    db_module._SessionLocal = sessionmaker(bind=db_module._engine, autocommit=False, autoflush=False)
+    Base.metadata.create_all(db_module._engine)
+    yield db_module._engine
+    Base.metadata.drop_all(db_module._engine)
+    db_module._engine = None
+    db_module._SessionLocal = None

backend/tests/test_project_task_recovery.py

@@ -1,31 +1,56 @@
+# backend/tests/test_project_task_recovery.py
+"""
+Tests per a la garantia que active_task_id es persisteix i es recupera.
+Equivalent als tests originals sobre Project.to_dict/from_dict,
+ara adaptats a ProjectManager + BD SQLAlchemy.
+"""
+import pytest
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from backend.app.db import Base
+import backend.app.db as db_module
+import backend.app.models.db_models  # registra tots els models ORM
+
+
+@pytest.fixture(autouse=True)
+def isolated_db():
+    """BD SQLite en memòria per a cada test."""
+    db_module._engine = create_engine("sqlite:///:memory:", connect_args={"check_same_thread": False})
+    db_module._SessionLocal = sessionmaker(bind=db_module._engine, autocommit=False, autoflush=False)
+    Base.metadata.create_all(db_module._engine)
+    yield
+    Base.metadata.drop_all(db_module._engine)
+    db_module._engine = None
+    db_module._SessionLocal = None
+
+
 def test_project_serializes_active_task_id():
-    """active_task_id is included in Project.to_dict()."""
-    from app.models.project import Project, ProjectStatus
-    p = Project(
-        project_id="proj-1", name="Test",
-        status=ProjectStatus.GRAPH_BUILDING,
-        created_at="2026-01-01", updated_at="2026-01-01",
-        active_task_id="task-abc-123",
-    )
-    assert p.to_dict()["active_task_id"] == "task-abc-123"
+    """active_task_id es pot desar i recuperar del ProjectManager."""
+    from backend.app.models.project import ProjectManager
+    proj = ProjectManager.create_project("Test")
+    ProjectManager.save_project({
+        "id": proj["id"],
+        "active_task_id": "task-abc-123",
+    })
+    fetched = ProjectManager.get_project(proj["id"])
+    assert fetched["active_task_id"] == "task-abc-123"
 
 
 def test_project_deserializes_active_task_id():
-    """Project.from_dict() restores active_task_id from JSON."""
-    from app.models.project import Project
-    data = {
-        "project_id": "proj-1", "name": "Test", "status": "graph_building",
-        "created_at": "2026-01-01", "updated_at": "2026-01-01",
-        "active_task_id": "task-abc-123",
-    }
-    assert Project.from_dict(data).active_task_id == "task-abc-123"
+    """active_task_id es restaura correctament des de la BD."""
+    from backend.app.models.project import ProjectManager
+    proj = ProjectManager.create_project("Test")
+    ProjectManager.save_project({
+        "id": proj["id"],
+        "active_task_id": "task-abc-456",
+    })
+    # Simulem que es torna a llegir (com si el servidor hagués reiniciat)
+    fetched = ProjectManager.get_project(proj["id"])
+    assert fetched["active_task_id"] == "task-abc-456"
 
 
 def test_project_active_task_id_defaults_none():
-    """active_task_id defaults to None for projects without it (backward compat)."""
-    from app.models.project import Project
-    data = {
-        "project_id": "proj-1", "name": "Test", "status": "created",
-        "created_at": "2026-01-01", "updated_at": "2026-01-01",
-    }
-    assert Project.from_dict(data).active_task_id is None
+    """active_task_id és None per a projectes creats sense task (compatibilitat enrere)."""
+    from backend.app.models.project import ProjectManager
+    proj = ProjectManager.create_project("Test")
+    assert proj["active_task_id"] is None